NEMISTRY 


PAPER -MAKING 


THE 


CHEMISTRY 


OF 


PAPER-MAKING 

TOGETHER  WITH  THE 

PEINCIPLES  OF  GENERAL  CHEMISTRY 


A  HANDBOOK  FOR  THE  STUDENT  AND  MANUFACTURER 

BY 
E.  B.  GRIFFIN  AND.  A.  D.  LITTLE 


NEW  YORK 

HOWARD  LOCKWOOD   &   CO. 
1894 


• 


Entered  according  to  Act  of  Congress,  in  the  year  1894,  by  HOWARD  LOCKWOOD  &  Co. 
in  the  office  of  the  Librarian  of  Congress  at  Washington. 


PREFACE. 


A  CONSIDERABLE  part  of  this  book  has  been  devoted  to  the 
elementary  facts  and  principles  of  general  chemistry  and  to  proc- 
esses of  chemical  analysis  which  are,  in  the  main,  well  known,  in 
the  hope  that  the  strictly  technical  portion  might  thus  be  ren- 
dered more  available  to  the  large  body  of  paper-makers  whose 
knowledge  of  i^he  science  is  limited.  For  this  reason  the  Intro- 
duction treats  briefly  of  chemical  theory,  while  Part  I.  contains 
a  short  account  of  the  different  elements  and  a  reference  to  their 
more  important  compounds.  In  Chapter  VIII.  the  various 
analytical  processes  which  are  employed  in  the  examination  of 
paper-making  materials  are  given  at  some  length. 

Among  the  numerous  authorities  consulted  special  mention 
should  be  made  of  Goodale's  "  Vegetable  Physiology,"  Sargeant's 
"Keport  on  the  Forest  Trees  of  North  America,"  Schubert's 
"Die  Cellulosef abrikation, "  the  very  complete  reports  of  the 
State  Board  of  Health  of  Massachusetts  in.  connection  with  the 
subject  of  water,  and  files  of  "THE  PAPER  TRADE  JOURNAL" 
and  Hofmann's  Papier- Zeitung.  The  excellent  plate  of  fibres 
is  from  the  valuable  little  book  by  Dr.  W.  Herzberg"  entitled 
"Papier-Prufung,"  in  which  also  may  be  found  many  of  the 
facts  relating  to  the  German  methods  of  paper- testing.  The 
niimerous  papers  and  reports  of  Cross  and  Bevan  on  cellulose, 
fibres,  and  the  processes  of  paper-making  have  been  freely  drawn 

upon. 

iii 


38 


iv  PREP" AGE 


This  opportunity  is  taken  to  thank  collectively  the  many 
friends  in  the  paper  trade  who  have  kindly  contributed  the 
results  of  their  experience  and  permitted  the  publication  of 
analyses  made  in  our  laboratory  for  them.  Valuable  assistance 
has  also  been  received  in  various  ways  from  Messrs.  A.  Wendler, 
E.  C.  Albree,  J.  L.  Hecht,  George  T.  Cooke  and  Dr.  Frederick 
Fox. 

The  death  of  my  friend  and  partner  deprived  rno  of  his 
co-operation  when  tire  book  was  only  partially  completed,  and 
has  at  many  points  obliged  me  to  forego  that 'fullness  of  treat- 
ment which  his  aid  would  have  rendered  easy. 

A.  D.  LITTLE. 
BOSTON,  August,  1894. 


CONTENTS. 


PA-.K 

INTRODUCTION— -PRINCIPLES  OF  CHEMICAL  THEORY    .......        8 


PART  I. 

GENERAL   CHEMISTRY. 

•  > 

THE  NON-METALLIC  ELEMENTS 25 

THE  METALLIC  ELEMENTS .  62 

PART  n. 

HE   CHEMISTRY   OF   PAPER-MAKING- 
CHAP. 

I.  CELLULOSE 103 

II.  FIBRES 117 

III.  PROCESS  FOR  ISOLATING  CELLULOSE       ...  151 

Rag  Boiling 151 

r  • 

Treatment  of  Picker  Seed  and  Picker  Waste 15(3 

Esparto 157 

Straw 158 

MANUFACTURE  OF  WOOD  FIBRE:  — 

The  Soda  Process 161 

The  Sulphate  Process 178 

The  Sulphite  Process 17.9 

Theory 182 

History 185 

Preparing  Wood 188 

Liquor-making 190 

Digesters  and  Linings 232 

Boiling 250 

Recovery  of  Gas     ..'..' 261 

The  Waste  Liquor 270 

v 


vi  CONTENTS. 


IV.  BLEACHING 275 

V.  SIZING  AND  LOADING 301 

VI.  COLORING 320 

VII.  WATER 329 

VIII.  CHEMICAL  ANALYSIS -J.  .' 348 

IX.  PAPER-TESTING 420 

X.  ELECTROLYTIC  PROCESSES  ,  .  .  .  452 


APPENDIX  .    .    .    .    < 463 

INDEX ,    .   "     503 


THE 
CHEMISTRY    OF   PAPER-MAKING. 


THE 

CHEMISTRY   OF   PAPER-MAKING. 

INTRODUCTION. 

Physical  and  Chemical  Change. —  The  action  of  force  upon 
matter  gives  rise  to  changes  which  are  called  physical  or  chemical, 
according  as  the  identity  of  the  substance  acted  upon  is  preserved 
or  lost.  In  grinding  wood,  each  particle  of  the  pulp  remains  a  bit 
of  wood ;  in  beating  stock  or  forming  a  sheet  of  paper,  the  identity 
of  the  cellulose  is  not  affected.  Rosin  may  be  melted  or  broken 
down  to  powder,  but  its  character  as  rosin  remains  the  same.  Iron 
may  be  forged,  rolled,  filed  to  dust,  or  drawn  to  wire  along  which 
an.  electric  current  passes,  but  in  each  case  the  product  of  the 
process  is  iron.  All  of  these  changes  are  non-essential  ones  so  far 
as  the  identity  of  the  substances  is  concerned.  The  composition 
of  the  substances  has  been  unaffected  and  the  changes  are  physical 
ones. 

If  rags  are  boiled  for  some  hours  with  acid,  glucose  is  formed. 
Rosin  is  heated  with  soda,  and  a  size  which  is  d  ifferezit  from  either 
is  prepared.  Iron  rusts  in  the  air  or  burns  in  the  forge  or  dissolves 
in  acid,  and  the  products  would  never  be  confounded  with ,  the 
metal.  These  are  chemical  changes,  the  identity  of  thef  niateiiftls 
involved  in  them  has  been  lost,  and  new  and  different  sub- 
stances have  appeared.  The  changes  have  affected  the  ultinrate 
constitution  of  the  substances,  and  they  are  no  longer  what  they 
were.  It  is  with  such  changes  that  the  science  of  Chemistry  has 
to  deal. 

Conservation  of  Energy  and  Matter.  —  Chemistry,  in  the 
modern  sense,  began  with  the  recognition,  by  Lavoisier,  of  the  fact 
that  matter  is  never  destroyed  but  only  takes  on  new  forms.  If  a 
piece  of  charooal  is  burned  in  a  sealed  globe  large  enough  to  con- 
tain sufficient  air  for  the  combustion,  the  weight  of  the  globe 

3 


[CHEMISTS*   OF  PAPER-MAKING. 


remains  the  same  although  the  charcoal  has  disappeared.  So  in 
any  chemical  change  the  weight  of  the  products  of  the  reaction  is 
always  equal  to  the  weight  of  the  substances  first  concerned  in  it. 

This  law,  first  formulated  in  regard  to  matter,  has  more  recently 
been  shown  to  be  equally  true  of  energy  or  force.  Energy  is 
never  created  or  destroyed,  but  only  passes  from  one  form  of 
energy  into  its  equivalent  in  some  other  form  or  forms  of  energy. 
When  coal  is  burned,  the  energy  of  chemical  attraction  is  trans- 
formed into  the  energy  of  heat,  which  may  become  in  succession 
the  energy  of  steam,  of  a  moving  piston,  of  electricity  in  motion, 
to  be  again  transformed  into  light  and  heat.  Thes«  changes  are 
obscure,  the  force  which  is  available  for  our  uses  becomes  less 
with  each  transformation,  and  careful  experiments  which  take  into 
account  many  minor  changes  are  necessary  to  show  that  the  total 
amount  of  force  remains  the  same  through  each  successive  change. 

Weight  and  Volume.  —  Weight,  as  the  term  is  used  in  chem- 
istry, means  about  the  same  as  the  term  "  mass  "  in  ph}'sics  ;  that 
is,  it  is  used  to  denote  the  quantity  of  matter  which  a  body  con- 
tains as  compared  with  the  quantity  contained  in  some  other  body 
which  is  taken  as  the  unit  weight.  The  volume  of  a  body  is  the 
space  which  it  occupies,  and  volumes  are  given  in  terms  of  some 
unit  of  volume.  Much  of  what  chemistry  has  to  teach  rests  upon 
the  accuracy  of  our  determinations  of  these  two  functions  of 
matter,  and  it  is  therefore  of  the  first  importance  that  the  units 
employed  should  be  as  definite  and  convenient  as  possible.  For 
this  reason  the  French  system  of  measurement,  known  as  the 
metric  system,  has  been  universally  adopted  by  chemists,  and'the 
student  should  familiarize  himself  with  it  at  the  first  opportunity. 
This  rteed  require  very  little  time,  as  the  systom  is  extremely 
simple.  The  tables  will  be  found  in  the  Appendix,, 

Specific  Gravity.  —  The  specific  gravity  (or  Sp.  Gr.)  of  a  sub- 
stance is  the  ratio  between  the  weight  of  a  given  volume  of  the 
substance  and  the  weight  of  the  same  volume  of  some  other 
substance  which  is  selected  as  the  standard.  Water,  at  its  tem- 
perature of  greatest  density,  4°  O.,  is  the  substance  usually  taken 
for  the  standard  in  determining  e  Sp.  Gr.  of  liquids  and  solids, 
and  we  therefore  mean  in  saying  that  the  Sp.  Gr.  of  sulphuric 
acid  is  1.84,  of  lead  11.36,  of  alcohol  0.792,  that  these  substances 
are  respectively  1.84,  11.36,  and  0.792  times  as  heavy  as  water  at 
4°  C,,  volume  for  volume.  In  some  cases,  for  greater  convenience, 


INTRODUCTION. 


water  at  the  ordinary  temperature,  15°  C.,is  taken  as  the  standard, 
but  where  this  temperature  has  been  adopted  the  fact  is  usually 
stated  in  giving  the  Sp.  Gr.  Various  tables  of  Sp.  Gr.  will  be 
found  in  the  Appendix. 

The  specific  gravity  or  vapor  density  of  gases  and  vapors  is 
usually  referred  either  to  hydrogen,  because  it  is  the  lightest  of 
them  all,  or  else  to  air,  because  it  is  most  convenient.  In  this 
book,  unless  otherwise  stated,  the  standard  is  hydrogen. 

The  Atomic  Theory.  —  The  facts  of  chemistry  are  best  ex* 
plained  upon  the  theory,  first  propounded  in  its  present  form  by 
Dalton,  that  all  matter  is  composed  of  extremely  minute  particles 
called  Molecules.  A  molecule  is  the  smallest  particle  of  a  substance 
which  can  exist  and  still  remain  that  substance.  The  molecules 
are  themselves  believed  to  be  composed  of  still  smaller,  indivisible 
particles  called  Atoms,  and  these  particles  or  atoms  are  the  ulti- 
mate units  with  which  chemistry  deals  and  upon  which  chemical 
forces  are  exerted.  The  molecules  of  a  compound  substance  con- 
tain two  or  more  tiSMMMBfeti?  atoms,  which,  by  their  associa- 
tion and  arrangement,  give  rise  to  the  properties  which  distinguish 
the  substance.  When,  therefore,  by  any  chemical  process  the 
molecule  is  broken  up,  the  atoms  composing  it  arrange  themselves 
in  other  groups,  and  new  substances  result.  The  molecules  of 
those  simpler  forms  of  matter,  called  by  chemists  Elements,  contain 
atoms  of  only  a  single  kind,  but,  except  in  one  or  two  instances  to 
be  referred  to  in  due  course,  the  association  of  two  or  more  atoms 
in  the  molecule  is  necessary  to  establish  the  qualities  which  char- 
acterize the  elemental  substance ;  and  if  the  integrity  of  the 
molecule  is  impaired,  the  atoms  group  themselves  with  other  atoms 
to  form  new  molecules,  and  again  new  substances  are  formed. 

Properties  of  Matter.  —  The  different  kinds  of  matter  exhibit 
the  widest  possible  range  of  qualities.  The  words  hard,  soft,  light, 
heavy,  crystalline,  ductile,  brittle,  elastic,  volatile,  call  to  mind  as 
many  distinct  qualities.  The  physical  properties,  like  those  named, 
depend  mainly  upon  the  relations  of  the  molecules  to  each  other 
in  the  substance.  Chemical  properties  are  those  exhibited  by  a 
substance  in  its  relations  to  other  substances.  Thus  a  substance 
may  be  'inflammable  or  non-inflammable,  acid  or  alkaline,  soluble 
or  the  reverse,  in  various  liquids.  Chemical  properties  depend  upon 
the  number  and  kind  of  atoms  which  compose  the  molecule,  and 
upon  their  arrangement  within  the  molecule. 


THE  CHEMISTRY  OF  PAPER-MAKING. 


States  of  Matter.  —  Matter  may  exist  as  a  solid,  a  liquid,  or  a 
gas,  and  a  very  large  number  of  substances  may  be  made  to  assume 
one  state  or  the  other  at  will.  All  gases  may  be  reduced  to  liquids 
and  even  to  the  solid  form  by  the  combined  action  of  cold  and 
pressure.  The  essential  difference  between  the  three  states  is 
found  in  the  amount  or  range  of  movement  which  the  molecules 
of  a  substance  possess.  The  molecules  of  a  substance  are  not 
packed  together  like  the  cells  in  a  honeycomb,  but  are  separated 
by  spaces  which  are  undoubtedly  great  in  comparison  with  the  size 
of  the  molecules.  The  whole  great  group  of  molecules  which  con- 
stitutes a  bocly  is  held  together,  in  a  solid  or  liquid,  by  the  force 
called  Cohesion  exerted  between  the  molecules,  and  which  in  its 
final  terms  is  probably  similar  in  kind  to  the  force  which  holds  the 
sun  and  planets  together.  Like  the  stars,  the  molecules  and  atoms 
are  in  ceaseless  motion.  In  a  solid  this  motion  is  so  limited  by 
cohesion  that  the  molecules  preserve  their  positions  relative  to 
each  other,  and  resist  any  force  tending  to  displace  them.  In  a 
liquid  the  molecular  motion  is  so  much  greater  that  the' cohesive 
force  is  nearly  overcome.  Still  liquids  have  a  definite  surface,  and 
when  conditions  permit  assume  a  spherical  form.  In  a  gas  the 
molecules  move  still  more  freely,  and  there  is  no  cohesion  between 
the  molecules.  The  molecules  of  a  gas  tend  to  diffuse  equally  in 
all  directions. 

Differences  in  what  we  call  the  temperature  of  a  body  are  differ- 
ences in  the  momentum  of  the  moving  molecules.  These  differ- 
ences are  measured  in  an  arbitrary  way  by  the  thermometer.  When 
we  heat  a  body  we  expend  force  upon  it  to  increase  the  momentum 
of  its  molecules,  and  conversely,  when  a  body  is  cooled,  the  momen- 
tum of  its  molecules  is  gradually  distributed  among  those  of  the 
cooling  agent. 

Change  of  State.  —  Bearing  the  facts  of  the  last  two  para- 
graphs in  mind,  it  becomes  evident  how,  through  the  action  of 
heat,  a  solid  body  may  be  converted  into  a  liquid  and  finally  into 
a  gas ;  and  also  how  the  volume  of  a  substance  increases  as  its 
temperature  rises. 

In  order  to  bring  about  this  change  from  the  solid  to  the  liquid 
state,  or  from  the  liquid  to  the  gaseous  state,  it  is  necessary  to 
move  the  molecules  apart  sufficiently  to  limit  in  the  first  case,  and 
entirely  overcome  in  the  second,  the  force  of  cohesion.  This  is 
accomplished  by  the  power  supplied  by  heat.  In  other  words, 


1NTROD  UCTION. 


heat  is  absorbed  during  both  these  changes.  Ice  at  zero  centi- 
grade may  be  heated  for  some  time,  and  the  result  is  water  at 
zero.  Water  at  100°  C.  requires  much  heat  to  convert  it  into 
steam  at  100°  C.  The  heat  thus  absorbed  is  given  out  again 
when  the  molecules  resume  their  former  positions,  and  is  therefore 
called  Latent  Heat.  Different  substances  have  different  latent 
heats.  Similarly,  equal  weights  of  different  substances  require 
different  quantities  of  heat  to  produce  the  same  rise  of  tem- 
perature. Water  requires  more  than  almost  any  other  substance, 
and  the  quantity  of  heat  needed  to  raise  one  kilogramme  (2.2  Ibs.) 
from  0°  to  1°  C.  is  called  one  unit  of  heat.  It  is  the  moving  force 
developed  by  423  kilogrammes  falling  one  metre  (3  ft.  8f  in.). 
The  Specific  Heat  (A  a  substance  is  the  proportion  between  the 
quantity  of  heat  needed  to  raise  the  temperature  of  a  given  weight 
of  the  substance  through  one  degree  and  the  quantity  of  heat 
needed  to  raise  the  temperature  of  an  equal  weight  of  water 
through  one  degree. 

Gas  Pressure.  —  Since  the  molecules  of  a  gas  are  free  to  move 
in  straight  paths,  it  follows  that  the  molecules  are  constantly 
bombarding  the  walls  of  any  containing  vessel.  These  blows,  by 
their  aggregate  effect,  produce  the  phenomena  of  gas  pressure.  If 
the  rapidity  of  motion  is  increased  by  heat,  the  impacts  are  more 
violent  and  the  pressure  rises.  If  the  volume  of  the  vessel  is 
decreased,  more  molecules  strike  the  walls  and  the  pressure  simi- 
larly rises.  The  power  of  the  steam-engine  is  derived  from  the 
blows  delivered  against  the  piston  by  the  infinite  number  of  mole- 
cules of  water  as  their  motion  is  .arrested  by  its  face. 

Compounds  and  Elements.  — -  By  the  processes  of  chemical 
analysis  nearly  every  known  substance  may  be  made  to  yield  two 
or  more  simpler  bodies.  Substances  which  may  be  thus  decom- 
posed are  termed  Compounds.  About  seventy  substances  are 
known  to  chemists  which  have  so  far  resisted  all  attempts  to 
resolve  them  into  anything  simpler.  Such  simple  substances 
are  called  Elements.  The  elements  exhibit  every  diversity  of 
character.  Some,  like  oxygen  and  chlorine,  are  gases ;  others, 
like  bromine  and  mercury,  are  liquids  at  ordinary  temperatures. 
The  great  majority  are  solids.  Only  about  one-half  of  them  are 
of  common  occurrence. 

The  Law  of  Ampere.  —  Various  experimentalists  have  shown 
that  all  gases  expand  and  contract  equally  under  the  same 


8  THE  CHEMISTRY  OF  PAPER-MAKING. 

variations  of  temperature  and  pressure.  From  this  fact  it  follows, 
as  a  mathematical  consequence,  that  equal  volumes  of  all  gases, 
under  the  same  conditions  of  temperature  and  pressure,  contain  the 
same  number  of  molecules.  This  deduction,  which  is  of  great 
importance  in  the  theory  of  chemistry,  is  called  the  Law  of 
Ampere. 

Atomic  "Weights.  —  In  order  that  chemical  calculations  may  be 
accurately  performed,  it  is  of  the  first  importance  that  the  relative 
weights  of  the  atoms  composing  the  different  elementary  sub- 
stances should  be  accurately  determined,  since  combination  takes 
place  between  atoms.  Hydrogen  is  the  lightest  of  all  known 
substances,  and  the  weight  of  the  hydrogen  atom  is  therefore 
taken  as  the  unit  in  which  the  weights  of  all  the  other  atoms  are 
expressed.  The  atomic  weight  of  oxygen  is  given  as  16  —  this 
means  that  an  atom  of  oxygen  is  16  times  as  heavy  as  an  atom  of 
hydrogen.  The  molecular  weight  of  a  substance  is  the  sum  of  the 
weights  of  the  atoms  which  compose  the  molecule,  and  is  of  course 
dependent  upon  the  number  and  kind  of  atoms  which  the  molecule 
contains.  A  table  giving  the  atomic  weights  of  the  different 
elements  will  be  found  in  the  Appendix. 

Although  these  weights  are  only  relative  weights,  they  are  none 
the  less  real,  and  many  of  them  have  been  determined  with  the 
most  refined  accuracy.  Their  value  rests  upon  data  of  several 
kinds,  and  which  are  in  large  measure  independent  of  each  other. 
First,  the  law  of  Ampere  gives  us  a  means  of  finding  the  molecular 
weight  of  any  substance  which  can  be  brought  into  the  state  of 
gas.  We  know  by  the  results  of  chemical  analysis  that  the 
molecule  of  hydrogen  contains  two  atoms,  and  that  its  molecular 
weight  is  therefore  2.  Since  equal  volumes  of  different  gases 
contain  the  same  number  of  molecules*  it  follows  that  the  molecular 
weight  of  any  substance  is  equal  to  twice  its  specific  gravity  in 
the  state  of  gas.  For  example,  oxygen  is  16  times  as  heavy  as 
hydrogen,  volume  for  volume ;  that  is,  the  Sp.  Gr.  of  oxygen  is 
16,  and  the  oxygen  molecule  must  weigh  16  times  as  much  as 
the  hydrogen  molecule :  16  X  2  =  32,  the  molecular  weight  of 
oxygen. 

Second,  by  analysis  of  the  different  compounds  of  an  element, 
and  comparison  of  the  results,  we  are  able  to  find  those  compounds 
in  which  the  element  enters  into  combination  in  smallest  propor- 
tion, and  such  compounds  are  therefore  believed  to  contain  only 


INTRODUCTION.  9 

one  atom  of  this  element  in  a  molecule  of  the  compound.  Tims 
twice  the  Sp.  Gr.  of  hydrochloric  acid  gas  gives  36.5  as  the  molec- 
ular weight,  and  36.5  parts  of  the  acid  by  weight  yield  one  part 
of  hydrogen.  None  of  the  immense  number  of  hydrogen  com- 
pounds yield  on  analysis  less  than  one  part  by  weight  of  this  ele- 
ment, where  amounts  which  are  proportional  to  the  molecular 
weight  of  the  compounds  are  taken  for  analysis.  Some  give  two, 
three,  four,  or  more  times  this  quantity,  and  are  therefore  believed 
to  contain  two,  three,  four,  or  more  atoms  of  hydrogen  in  the  mole- 
cule, as  the  case  may  be. 

Third,  we  find,  for  example,  that  one  volume  of  hydrogen  com- 
bines with  one  volume  of  chlorine  to  form  two  volumes  of  hydro- 
chloric acid  gas;  therefore  one  molecule  of  hydrogen  combines  with 
one  molecule  of  chlorine  to  form  two  molecules  of  hydrochloric 
acid.  This  acid  contains  the  smallest  proportion  of  chlorine  which 
enters  into  combination,  as  well  as  the  smallest  proportion  of 
hydrogen ;  that  is,  one  molecule  of  the  acid  contains  an  atom  of 
hydrogen  and  an  atom  of  chlorine.  It  follows,  then,  that  if  one 
molecule  of  hydrogen  forms,  with  one  molecule  of  chlorine,  two 
molecules  of  the  acid,  the  molecule  of  each  element  must  contain 
two  atoms.  Twice  the  Sp.  Gr.  of  chlorine  gas  is  71,  which  is  the 
weight  of  this  molecule  containing  two  atoms.  The  weight  of  the 
single  atom  is  therefore  35.5,  and  no  compound  of  chlorine  is  known 
which  does  not  give  this  quantity  or  some  multiple  of  it,  when 
an  amount  proportional  to  the  molecular  weight  of  the  compound 
is  analyzed. 

Fourth,  the  relations  of  the  atoms  to  heat  furnish  another  means 
by  which  the  atomic  weights  may  be  checked,  since  it  is  true  that 
the  quantity  of  heat  required  to  raise  the  temperature  of  an  atom 
one  degree  is  the  same  for  all  atoms.  We  believe  that  16  grammes 
of  oxygen  contain  as  many  atoms  as  one  gramme  of  hydrogen,  since 
an  atom  of  oxygen  is  believed  to  be  16  times  as  heavy  as  one  of 
hydrogen.  If  this  belief  is  correct,  it  should  require  the  same 
amount  of  heat  to  raise  the  temperature  of  a  gramme  of  hydrogen 
one  degree  as  to  raise  the  temperature  of  16  grammes  of  oxygen 
one  degree,  and  experiment  proves  that  such  is  the  case. 

The  L.aw  of  Definite  Proportions.  —  Chemical  combination 
always  takes  place  in  definite  proportions,  and  such  proportions 
appear  whether  we  regard  the  weights  of  the  substances  concerned 
or  their  volumes  in  the  state  of  gas.  In  this  fact  is  found  one  of 


10  THE  CHEMISTRY  OF  PAPER-MAKING. 

the  strongest  proofs  of  the  correctness  of  the  atomic  theory,  for 
the  fact  c&n  only  be  explained  upon  the  assumptions  that  combina- 
tion takes  place  between  atoms  and  that  the  atoms  have  definite 
weights.  Two  volumes  of  hydrogen  combine  with  one  volume  of 
oxygen  to  form  two  volumes  of  steam,  and  the  law  of  Ampere 
points  out  the  simple  numerical  relation  existing  between  the 
number  of  molecules  of  each  substance  and  consequently  between 
the  number  of  atoms  concerned.  If  by  accident  or  design  any 
excess  of  either  gas  is  present,  it  remains  unchanged.  Since  the 
atoms  have  definite  weights,  combination  between  them  must 
always  take  place  in  a  definite  proportion  by  weight.  A  molecule 
of  water  always  contains  two  atoms  of  hydrogen,  and  one  atom  of 
oxygen  and  18  parts  by  weight  of  water  must  therefore  always 
yield  two  parts  by  weight  of  hydrogen  and  16  parts  by  weight 
pf  oxygen. 

Mixtures  and  Chemical  Compounds.  —  The  facts  of  the  last 
paragraph  enable  us  to  determine  whether  a  substance  under  exam- 
ination is  a  mixture  or  a  chemical  compound.  The  proportions  of 
the  different  substances  which  enter  into  a  chemical  compound  are 
always  fixed  and  definite,  and  £he  compound  itself  is  different  from 
either  or  any  of  its  components.  Heat,  moreover,  is  usually  devel- 
oped when  substances  combine  chemically.  Mixtures  may  take 
place  in  all  proportions  ?  no  heat  is  developed  unless  there  is  some 
accompanying  chemical  action,  and  the  properties  of  the  mixture 
bear  some  obvious  relation  to  those  of  its  ingredients.  Simple  me- 
chanical means  are  usually  sufficient  to  separate  a  mixture.  Gun- 
powder, for  example,  is  a  very  perfect  mixture  of  sulphur,  nitre,  and 
charcoal.  The  proportion  of  each  varies  with  the  country  and  pur- 
pose for  which  the  powder  is  made.  The  separate  particles  of  each 
component  may  be  distinguished  under  the  microscope.  Mere  wash- 
ing with  water  will  remove  the  nitre,  and  the  sulphur  may  be  dis- 
solved in  bisulphide  of  carbon,  leaving  the  charcoal  by  itself.  When 
the  powder  is  exploded,  chemical  compounds  are  formed  which 
differ  completely  in  their  character  from  any  of  the  ingredients  of 
powder,  and  if  more  charcoal,  for  example,  is  present  than  was 
needed  to  form  these  compounds,  the  excess  will  remain  as  char- 
coal until  it  reaches  the  air. 

Chemical  Symbols. — In  order  to  represent  the  constitution  of 
substances  as  clearly  and  concisely  as  possible,  chemists  have 
adopted  a  system  of  notation  in  which  the  initial  letter  of  the 


INTRODUCTION.  11 


Latin  name  of  the  different  elementary  substances  is  made  to 
represent  one  atom  of  the  element.  Thus  one  atom  of  hydrogen 
is  represented  by  H  ;  one  atom  of  sulphur,  by  S ;  oneutomof  oxygen, 
by  O.  Where  several  elements  would  otherwise  have  the  same 
symbol,  an  additional  letter  is  added  to  avoid  confusion.  C  stands 
for  one  atom  of  carbon ;  Gl,  for  an  atom  of  chlorine ;  Na,  for  an 
atom  of  sodium  (natrium).  A  table  of  the  elements,  giving  their 
symbols  and  atomic  weights,  will  be  found  in  the  Appendix, 

When  it  is  wished  to  represent  several  atoms  of  the  same  kind, 
the  appropriate  figure  is  placed  to  the  right  of  and  below  the 
symbol ;  thus,  H2  represents  two  atoms  or  a  molecule  of  hydrogen ; 
S6,  six  atoms  of  sulphur.  The  composition  of  a  compound  sub- 
stance is  shown  by  grouping  together  the  symbols  of  its  component 
atoms  with  the  figures  showing  the  number  of  each  kind  of  atom ; 
thus,  HC1  stands  for  one  molecule  of  hydrochloric  acid,  and 
shows  that  the  molecule  is  composed  of  an  atom  of  hydrogen 
and  an  atom  of  chlorine;  HaO  stands  for  water  or  a  molecule 
of  water,  which  contains  two  atoms  of  hydrogen  and  one  of 
oxygen ;  H2SO4  stands  for  a  molecule  of  sulphuric  acid,  which  is 
composed  of  two  atoms  of  hydrogen,  one  of  sulphur,  and  four  of 
oxygen. 

In  order  to  represent  several  molecules  of  the  same  substance 
it  is  customary  to  use  a  large  figure  on  the  line  and  to  the  left  of 
the  symbols  which  represent  a  single  molecule ;  thus,  2  Na2OQ3 
stands  for  two  molecules  of  soda-ash.  Parentheses  and  a  small 
number  to  the  right  are  sometimes  used  for  the  same  purpose; 
thus,  (Na2CO3)2:  but  this  form  is  usually  limited  to  cases  where 
the  symbols  or  formulas  of  several  different  molecules  are  grouped 
together,  and  the  small  number  outside  the  parenthesis  indi- 
cates that  everything  inside  the  parenthesis  is  to  be  multiplied 
accordingly. 

Since  the  atoms  have  definite  weights,  the  symbol  which 
represents  the  number  and  kinds  of  atoms  in  a  molecule  alao 
represents  the  proportion  by  weight  in  which  each  element  occurs 
in  the  molecule ;  and  since  the  mass  of  a  compound  is  made  up 
of  similar  molecules  the  symbol  also  stands  for  the  kinds  and 
proportions  of  the  elementary  substances  composing  the  compound 
substance.  For  example,  in  the  case  of  the  symbol  Na2CO8  just 
given  for  soda-ash,  a  reference  to  the  table  of  atomic  weights 
shows  that  the  atomic  weight  of  sodium,  Na,  is  23 ;  of  carbon,  12 ; 


12  THE  CHEMISTRY  OF  PAPER-MAKING. 

of  oxygen,  16.  The  proportion  by  weight  in  which  the  different 
elements  occur  in  the  molecule  is  then :  — 

Sodium,  Na    ...;....     23  x  2  =  46 

Carbon,  C 12  x  1  =  12 

Oxygen,  O 16x3  =  48 

106 

The  molecular  weight  of  soda-ash  (sodium  carbonate)  is  therefore 
106,  End  in  the  molecule  there  are  46  parts  by  weight  of  the  metal 
sodium,  12  parts  of  carbon,  and  48  parts  of  oxygen.  Any  quantity 
of  sodium  carbonate  is  merely  an  aggregation  of  similar  molecules, 
and  therefore  the  proportions  by  weight  which  are  true  of  the 
molecule  are  also  true  of  any  quantity  of  the  compound. 

Chemical  symbols,  furthermore,  indicate  the  proportions  in 
which  combination  by  volume  occurs  when  the  substances  are  in 
the  state  of  gas ;  for,  bearing  the  law  of  Ampere  in  mind,  each 
molecule  represented  by  the  symbols  represents  a  unit  volume  of 
the  gas. 

2  mola.  of  hydrogen.     1  mo!,  of  oxygon.    2  mole,  of  steam. 

2H2         +         O2       =       2H2O 

or  two  volumes  of  hydrogen  combine  with  one  volume  of  oxygen 
to  form  two  volumes  of  steam. 

The  Law  of  Multiple  Proportions.  —  Among  the  compounds 
of  chlorine  there  are  four  which  are  known  to  have  the  composi- 
tion represented  by  »the  formulas :  — 

HC10,     HC102,     HC103,    HC1O4. 

These  are  the  only  'known  compounds  of  chlorine  which  contain 
these  three  elements  and  no  other.  Nearly  all  the  elements 
combine  with  each  other  in  more  than  one  proportion,  but  there 
is  always  in  such  cases  a  simple  numerical  ratio  between  the  pro- 
portions in  which  the  elements  occur  in  the  different  compounds. 
If  we  select  the  compound  containing  the  least  of  one  of  the 
elements  which  combines  thus  in  several  different  proportions,  the 
proportions  in  the  other  oases  are  simple  multiples  of  the  pro- 
portion present  in  the  one  selected.  In  the  case  given  above 
there  is  present  in  each  compound  35.5  parts  by  weight  of 
chlorine,  while  the  amount  of  oxygen  is,  as  the  compounds  are 
successively  considered,  16,  32,  48,  64  parts  by  weight,  and  these 
numbers  bear  the  same  ratio  as  1,  2,  3,  4.  This  law  of  multiple 


INTRODUCTION.  13 


pro  portion  Si  though  first  shown  by  the  results  of  chemical  analysis, 
is  an  evident  consequence  of  the  fact  that  combination  always 
takes  place  between  atoms. 

Chemical  Equivalents.  —  The  same  quantit}r  of  any  acid  which 
is  needed  to  neutralize  40  parts  by  weight  of  caustic  soda  will 
neutralize  28  parts  of  lime  or  20  parts  of  magnesia,  and  the  same 
quantity  of  any  of  these  alkalis  which  will  neutralize  36.5  parts 
by  weight  of  gaseous  hydrochloric  acid  will  neutralize  49  parts  of 
sulphuric  acid  or  63  parts  of  nitric  acid.  Quantities  of  different 
substances  which  are  found  by  experiment  to  stand  in  this  relation 
to  each  other  are  termed  chemical  equivalents. 

Qnanti valence.  —  A  reference  to  the  symbols  given  below,  which 
of  course  represent  the  composition  of  the  compounds  as  determined 
by  analysis,  reveals  an  important  fact :  — 

HC1 Hydrochloric  acid 

H2O Water 

H3N  .......  Ammonia 

H4C Marsh  gas 

We  find,  that  whereas  an  atom  of  chlorine,  Cl,  combines  with  or 
fixes  one  atom  of  hydrogen,  H,  an  atom  of  oxygen,  O,  fixes  two, 
an  atom  of  nitrogen,  N,  fixes  three,  and  an  atom  of  carbon,  C,  fixes 
four  of  hydrogen.  This  attractive  or  atom-fixing  power,  which 
varies  with  the  atoms  of  different  elements,  is  termed  the  quan- 
ti  valence  of  the  atom.  An  atom  which  either  combines  with  or 
replaces  a  single  atom  of  hydrogen  is  called  a  univalent  atom; 
one  which  combines  with  or  replaces  two  atoms  of  hydrogen,  or 
another  univalent  substance,  is  termed  bivalent ;  if  the  fixing 
power  extends  to  three  or  four  atoms  of  a  univalent  substance,  the 
atom  is  trivalent  or  quadrivalent,  as  the  case  may  be. 

The  quantivalence  of  the  atoms  is  believed  to  be  due  to  a  sort  of 
polarity,  the  attractive  power  of  each  pole  being  sufficient  to  hold 
in  the  molecule  a  single  univalent  atom.  These  poles  or  bonds 
are  often  represented  by  short  lines  radiating  from  the  symbol  of 
the  atom,  and  the  symbols  given  above  are  then  written  thus :  — 

H  H 

I  I 

H-C1          H-O-H  H-N  H-C-H 

I  I 

H  H 


14  THE  CHEMISTRY  OF  PAPEE-MAKING. 


Just  as  the  two  poles  of  a  magnet  may  neutralize  or  satisfy  each 
other,  so,  under  certain  circumstances,  two  of  these  atomic  poles 
may  satisfy  each  other,  and  the  same  atom  may  in  its  different 
combinations  exhibit  different  atom-fixing  powers.  Thus  we  have  : 


.A  mmonia.  Chloride  of  ammonia. 

H  H 

H 


H  H 

and  the  two  chlorides  of  phosphorus  :  — 

Cl  Cl 

I  Cl      | 

CI-P  )  p_ci 

i  cr  \ 

ci  ci 

Manganese  and  fluorine  form  four  compounds,  and  the  proportions 
and  quantivalence  of  the  atoms  in  each  case  are  shown  in  the 
symbols  given  below  :  — 

F 
I 

F-Mn-F  F-Mn-F 

I 
F 

F       F  F    F 

I  i  \/ 
F-Mn-Hn-F                        F-Mn-F 

II  /\ 
F        F                                     F    F 

Since  whenever  the  quantivalence  varies,  two  poles  must  either 
neutralize  or  free  each  other,  the  atom-fixing  power  is  either 
always  even  or  always  odd,  and  a  comparison  of  all  the  symbols 
given  under  this  head  brings  out  this  fact.  Symbols,  like  those 
immediately  above,  are  called  Graphic  Symbols,  and  they  are  much 
used  to  represent,  as  clearly  as  may  be,  the  arrangement  of  the 
atoms  in  the  molecule. 

Nomenclature.  —  The  number  of  .substances  known  to  chem- 
istry is  so  immense  that  their  study  is  greatly  facilitated  by  a 
system  of  naming  them,  which  not  only  arranges  them  in  groups, 
but  indicates  their  composition.  The  names  of  all  the  more 


INTRODUCTION.  16 


recently  discovered  metals  end  in  -mm  or  -urn,  as  sodium,  potas- 
sium, platinum.  The  names  of  various  groups  of  non-metallic 
elements  .have  distinctive  endings,  as  carbon,  boron,  silicon  ;  chlo- 
fine,  bronuni,  iodine,  fluorwe.  In  many  cases,  however,  both 
among  metals  and  non-metals,  old  names  persist,  as  iron,  silver, 
sulphur,  phosphorus.  Compounds  of  oxygen  and  another  ele- 
ment are  called  oxides,  similar  compounds  of  sulphur  are  called 
sulphwfe*,  and  most  of  the  non-metallic  elements  form  with 
another  element  compounds  whose  names  end  in  -ide*  Thus 
chlorine,  bromine,  iodine,  fluorine  form  chlorides,  broim'tfes,  io- 
dides,  fluoride  respectively.  The  proportion  of  the  non-metallic 
element  present  is  indicated  by  the  prefixes  di-  (or  it-).,  tri-t  tetra-, 
penta-,  as  appears  in  the  examples  below  :  — 

Manganese  dioxide  .........  MnO3 

Phosphorous  trioxida  .......  .   .  P203 

Tin  tetrachloride     .     ........  SiiCl4 

Phosphorous  pentoxide    ....... 


The  different  atom-fixing  power  of  an  element  is-  often  indicated 
by  the  endings  -ous  and  -ic  of  its  Latin  name.  Thus  iron  (ferrum) 
forms  ferrous  chloride,  FeCl2,  and  ferric  chloride,  Fe2Cl6.  Tin 
(stannum)  forms  stannous  chloride,  SnClo,  and  stannic  chloride, 
SnCli  ;  and  in  such  names  -ous  indicates  the  lower  degree  of  atom- 
fixing  power  or  quantivalence,  and  -ic  the  higher. 

Compounds  of  the  metals  with  oxygen,  or  oxides  of  the  metals, 
are  called  Betsey  and  the  same  term  is  applied  to  compounds  of  the 
metals  with  oxygen  and  hydrogen  or  hydrates  of  the  metals.  The 
bases  possess,  in  a  more  or  less  marked  degree,  those  properties 
which  are  termed  alkaline.  They-  unite  with  acids  to  form  Salts. 

Compounds  of  the  non-metallic  elements  which,  contain  hydro- 
gen which  may  be  replaced  by  a  metal  are  termed  Acids. 
Hydrochloric  acid,  HC1,  for  example,  contains  an  atom  of  hydro- 
gen, which  may  be  replaced  by  a  metal,  like  sodiumi,  to  form,  in 
this  case,  sodium  chloride,  NaCl,  common  salt.  Sulphuric  acid 
contains  two  atoms  of  hydrogen,  which  may  be  thus  replaced  by 
two  univalent  atoms  like  sodium  to  form  sodium  sulphate,  NaaSO4, 
or  by  one  bivalent  atom  like  zinc  to  form  zinc  sulphate,  ZnSO4. 
An  acid  is  termed  monobasic,  dibasic,  and  so  on,  according  as  it 
contains  one,  two,  or  more  hydrogen  atoms  which  may  be  thus 
replaced.  Whether  the  hydrogen  atoms  can  be  replaced  by  a 


16  THE  CHEMISTRY  OF  PAPER-MAKING. 

metal  depends  on  their  position  in  the  molecule.  Acetic  acid, 
C2H4O2,  is  a  monobasic  acid;  while  oxalic  acid,  C2H2O4,  is  a  bibasic 
acid.  This  difference  is  shown  in  the  graphic  symbols  of  these 
compounds :  — 

Acetic  acid.  Oxalic  acid. 

OH  00 

II       |  II       it 

H-O-C-C-H  H-0-C-C-O-H 

I 
H 

It  will  be  noticed  that  three  of  the  hydrogen  atoms  in  acetic  acid 
are  shown  in  a  different  relation  to  the  carbon  atoms  than  that 
occupied  by  the  other  one,  and  we  find  by  experiment  that  these 
three  atoms  can  be  replaced  by  a  non-metallic  element  like 
chlorine,  but  not  by  a  metal.  The  graphic  symbol  is  deduced 
from  the  results  of  such  experiments.  In  the  molecule  of  oxalic 
acid,  however,  both  hydrogen  atoms  occupy  the  same  position 
relative  to  the  molecule  that  the  atom  of  hydrogen  which  can 
be  replaced  by  a  metal  occupies  in  acetic  acid.  Both  of  these 
atoms  can  be  replaced  by  a  metal,  but  not  by  a  non-metal  like 
chlorine. 

This  illustrates  again  the  general  truth  that  the  properties  of 
a  substance  depend  quite  as  much  upon  the  arrangement  of  the 
atoms  in  the  molecule  as  upon  the  number  and  kind  of  the  atoms 
themselves. 

Compounds  which  contain  no  hydrogen,  but  which  unite  with 
the  elements  of  water  to  form  bases  or  acids,  are  called  Anhydrides, 
the  word  meaning,  without  water.  Sulphuric  anhydride,  SO3,  for 
instance,  is  a  snow-like  solid  which  combines  with  water,  H2O,  to 
form  sulphuric  acid,  H<SO4. 

When  the  same  elements  combine  in  different  proportions  and 
form  more  than  one  acid,  the  suffix  -ous  is  used  to  indicate  the 
lower  stage  of  oxidation,  and  -ic  to  indicate  the  higher.  We  have 
chlorows  acid,  HC1O2,  which  forms  chlorates,  and  chloric  acid, 
HC1O8,  which  forms  chlorates.  In  case  there  are  other  acids  the 
prefixes  hypo-  and  per-  are  added,  the  first  to  indicate  the  lowest 
and  the  last  the  highest  stage  of  oxidation.  Thus  we  have  hypo- 
chlorous  acid,  HC1O,  which  forms  hypochlorites,  and  perchloric 
acid,  HC1O4,  which  forms  perchlorates. 


INTRODUCTION.  17 


Reactions  and  Equations.  —  The  changes  which  occur  when 
two  or  more  substances  react  upon  each  other  chemically,  or  when 
one  is  decomposed  by  heat  or  otherwise,  may  be  represented  by 
chemical  symbols  arranged  in  the  form  of  equations.  Caustic 
soda  and  hydrochloric  acid  combine  to  form  sodium  chloride  and 
water,  and  the  reaction  may  be  written  — 

Caustic  soda  +  Hydrochloric  acid  =  Sodium  chloride  +  Water. 

NaOH  +         HC1       =      NaCl      +  H2O. 

Upon  examining  this  equation,  and  any  properly  written  one,  we 
find  that  the  sum  of  the  atomic  weights  of  the  factors  on  one  side 
is  the  same  as  the  sum  of  the  atomic  weights  of  the  products  on 
the  other.  The  same  number  of  atoms  of*  each  kind  also  must 
appear  on  each  side  of  the  equation. 

It  must  be  borne  in  mind  that  these  equations  are  not  arbitrary 
formulas  which  the  atoms  are  expected  to  follow,  but  that  they  are 
written  to  express  what,  so  far  as  we  know,  actually  does  occur; 
and  such  an  equation,  to  be  useful,  must  take  into  account  the 
known  relations  and  chemical  properties  of  all  the  substances  con- 
cerned and  their  components. 

When  there  are  several  possible  reactions,  that  one,  if  any,  in 
which  a  gas  is  evolved,  or  an  insoluble  substance  formed,  is  the 
one  most  likely  to  occur.  Solution  in  a  liquid,  by  overcoming  the 
cohesion  of  the  molecules  and  leaving  them  more  free  to  move 
within  range  of  each  other's  influence,  promotes  chemical  change 
and  often  determines  the  course  of  the  reaction.  A  rise  of  tem- 
perature has  the  same  effect  in  promoting  chemical  activity,  because 
it  means  that  the  moving  power  of  the  molecules  is  increased.  At 
the  instant  in  which  an  atom  is  liberated  from  one  combination, 
and  before  it  has  entered  into  another,  the  atom  is  said  to  be  in  the 
nascent  state;  and  since  all  its  affinities  are  during  that  instant 
unsatisfied,  its  chemical  properties  are  thus  intensified.  For  ex- 
ample, in  the  reaction  of  sulphuric  acid  upon  zinc, — 

Zn  -f-  H,SO4  =  ZnSO4  +  H2, 

two  atoms  of  hydrogen  are  liberated  which  ordinarily  combine  at 
once  to  form  the  molecule  of  hydrogen,  H-H ;  but  if  another  sub- 
stance is  present  upon  which  the  just  liberated  atoms  can  react  be- 
fore mutually  satisfying  each  other,  they  are  likely  to  so  react  much 
more  powerfully  than  after  their  union  in  the  molecule  H-H. 


18  THE  CHEMISTRY  OF  PAPER-MAKING. 


When  an  electric  current  is  passed  through  water  the  following 
decomposition  occurs  :  — 


When  limestone,  calcium  carbonate,  CaCO3,  is  heated,  it  splits  up 
into  caustic  lime,  CaO,  and  free  carbonic  acid  gas,  thus  :  — 


CaC03  =  CaO  +  C02. 

Such  reactions,  in  which  a  substance  is  separated  into  two  or  more 
simpler  ones,  is  called  an  Analytical  Reaction;  and  analytical 
processes  are  those  which  seek  to  separate  a  substance  into  its 
constituents,  or  to  otherwise  determine  what  its  constituents  are. 
Synthetical  processes  are  those  by  means  of  which  a  substance  is 
transformed  into  another  more  complex  one  by  the  addition  of 
new  atoms  in  the  molecule.  The  following  are  examples  of 
synthetical  reactions  :  — 


=2HC1. 

There  is  another  very  common  form  of  reaction  in  which  certain 
of  the  atoms  merely  exchange  places  in  different  molecules.  For 
example,  in  the  manufacture  of  Pearl  Hardening  — 


Calcium  chloride  +  Sodium  suiphate 

CaCli       -I-     Ka2S04      =     2KaCl     4-       CaSO4. 

Stoehlometry.  —  When,  the  chemical  symbols  and  reactions  a  ra 
understood,  ordinary  chemical  calculations  require  only  the  applica- 
tion of  the  simplest  rules  of  arithmetic,  and  can  usually  be  solved 
by  the  rule  of  proportion.  The  following  rules  will  be  found  useful. 
The  relations  upon  which  they  depend  have  been  already  discussed 
in  the  preceding  sections. 

1.  The  molecular  weight  is  equal  to  the  sum  of  the  weights  of  the 
atoms  composing  the  molecule. 

2.  The  percentage  of  any  constituent  in  the  molecule  is  found  by 
multiplying  the  weight  of  the  constituent  by  100  and  dividing  by  the 
weight  of  the  molecule  ;  or, 

Wt.  of  constituent  :  Wt.  of  Mol.  =  a?  :  100. 


INTRODUCTION:.  19 


B.  The  proportion  of  any  ingredient  in  a  mass  of  a  compound  is 
the  same  as  the  proportion  of  the  ingredient  in  a  molecule  of  the 
compound. 

4.  In  any  chemical  reaction  the  total  weight  of  the  products  is 
equal  to  the  sum  of  the  weights  of  the  substances  first  concerned. 

5.  If  any  chemical  operation  is  expressed  in  the  form  of  an 
equation,  and  the  molecular  weights  of  all  the  substances  concerned 
are  then  written  below  their  respective  formulas,  the  following 
rule  will  be  found  sufficient  for  most  problems  :  — 

As  the  molecular  weight  of  the  substance  given  is  to  the  molecular 
weight  of  the  substance  required,  so  is  the  weight  (in  pounds, 
grammes,  etc.)  of  the  substance  given  to  the  weight  of  the  substance 
required. 

In  ease  the  equation  shows  that  more  than  one  molecule  of  a 
given  substance  is  concerned  in  it,  the  molecular  weight  of  that 
substance  should  be  multiplied  accordingly,  for  the  purposes  of  the 
above  rule. 

EXAMPLES. 

1.  What  is  the  molecular  weight  of  common  salt  ? 
Symbol  of  common  salt  is  NaCl. 

Ans.  Na  ==  23  ;  Cl  =  35.5  ;  NaCl  =  58.5. 

2.  What  is  the  molecular  weight  of  caustic  soda,  NaOH  ?     Ans.  40, 

3.  What  is  the  molecular  weight  of  sulphuric  acid,  H2S04  ?     Ans.  98. 

4.  What  is  the  molecular  weight  of  carbonate  of  soda,  soda-ash, 

Ans.  106. 


5.  What  is  the  molecular  weight  of  bisulphite  of  lime,  H2CaS2O6  ? 

Ans.  202. 

6.  How  much  chlorine  is  contained  in  1170  Ibs.  of  common  salt  ? 
Since  NaCl  =  58.5,  every  58.5  Ibs.  of  salt  contain  35.5  Ibs.  of  chlorine. 

Ans.  710  Ibs. 

7.  What  per  cent,  of  sulphur  is  there  in  sulphurous  acid  gas,  SO2  ? 

S  =  32,  0  =  16,  S02  =  32  -f  16  +  16  =  64. 
Wt.  of  S  32>:  wt.  of  SO2  64  =  x  :  100. 

32x100 

64  Ans.  50%. 


20  THE  CHEMISTRY  OF  PAPER-MAKING. 

8.  What  is  the  per  cent,  of  alumina,  A1203,  in  pure  crystallized  potash 
alum,  K2A12S4O16,  24  H2O  ? 

A12  27.4  x  2 ..=   54.8  K2  39.1  x    2  =   78.2 

O3 16.    X  3  =   48.  A12  27.4  x    2  =    548 

Mol.  wt.,Al203  =  102.8  S4S2.    x    4  =  128.0 

0*16.    x  16  =  256.0 
517.0 

24  H20  (2  -f  16)  x  24  =  432.0 
Mol.  wt.  potash  alum  =  949.0 
102.8  x  100      #  A10 

949          =  %  Al2°* '  Ans.  10.94 % 

9.  How  much  water,  H2O,  is  there  in  2000  Ibs.  of  crystallized  pot-ash 
alum? 

Ex.   8   shows  that  24  H20  =  432,  while   the   molecular  weight  of 
potash  alum  is  949. 

432  :  949  =  x :  2000.  Ans.  910.4  Ibs, 

10.  How  many  pounds  of  sulphurous  acid  gas  will  be  formed  by  the 
combustion  of  420  Ibs.  of  sulphur,  supposing  the  loss  of  sulphur  as  ash, 
and  by  sublimation,  to  amount  to  10  per  cent.  ? 

420  Ibs.  less  10%  =378  Ibs.  available. 

S  32 :  SO2  64  =  378  :  x.  Ans.  756  Ibs. 

11.  The   formula  of  Pearl  Hardening,  or  crystallized  sulphate  of 
lime,  as  it  occurs  in  paper,  is  CaSO4,  2  H20.     In  burning  the  paper  to 
determine  the  amount  of  filler,  this  combined  water  (2  H2O),  which 
really  adds  so  much  to  the  weight  of  the  paper,  is  driven  off,  so  that 
the  formula  of  the  ash  as  weighed  is  CaS04.     What  correction  should 
be  applied  to  the  per  cent,  of  ash  found  in  order  that  it 'may  show  the 
amount  of  Pearl  Hardening  really  in  the  paper  ? 

Mol.  wt.,  CaS04,  2  H2O^=  136  +  36  =  172  ; 
CaSO4  =  136. 

136  parts  of  ash,  CaSO4  =  172  parts  of  filler,  CaS04,  2  H2O. 
179 
~,  =*1.26 ;  therefore  every  1%  of  ash  =  1.26%  of  filler, 

and  per  cent,  of  ash  should  be  multiplied  by  1.26  in  order  to  obtain 
per  cent  of  filler  in  paper. 

12.  How  many  pounds  of  pure  sulphuric  acid,  H2S04,  are  needed  to 
dissolve  100  Ibs.  of  zinc,  the  reaction  being  — 

Zn  4-  H2SO4  =  ZnSQH-  H2? 
65         98 
The  proportion,  then,  is  65  :  98  =  100  :  x.  Ans.  151  Ibs. 


I-NTRODUCTION.  21 


13.  If  in  burning  420  Ibs.  of  sulphur  to  make  sulphite  liquor  10  per 
cent,  of  the  sulphur  is  converted  into  sulphuric  acid,  how  much  lime 
will  this  neutralize  in  forming  the  useless  sulphate  of  lime  ?     The 
reaction  may  be  considered  for  the  purposes  of  the  problem  — 

CaO  4-  H2SO4  =  CaSO4  +  H2O. 
56          98  Ans.  73.5  Ibs. 

14.  Thie  formula  of  soda-ash  is  Na^GO3;  of  soda  crystals,  Na  CQ8, 
10  H2O.     One  molecule  of  each  combines  with  the  same  amount  of 
rosin.     If  40  Ibs.  of  Na2COs-are  required  to  make  a  certain  quantity 
of  size,  how  much  Na2CO3,  10  H2O  will  be  needed  to  make  the  same 
amount  ?  Ans.  108  Ibs. 

15.  Lime,   CaO,   in   contact  with  water  slakes    to    form    calcium 
hydrate,  CaH2O2.     How  much  lime  would  be  required  to   causticize 
2000  Ibs.  of  soda-ash,  ]STa.,COs,  according  to  the  reaction  — 

Na.COj,  -f  GaH2O2  =  CaCO3  +  2  NaOH  ?        Ans.  1056.6  Ibs. 

16.  560  kilos  of  lime  are  required  to  make  a  certain  quantity  of 
sulphite  liquor.     How  many  kilos  of  limestone,  carbonate   of  lime, 
OaC03,  will  be  required  to  make  the  same  amount  of  liquor  ?     One 
molecule   of    lime  will  make  as   much    liquor  as  one   molecule  of 
limestone.  Ans.  1000  kilos. 


PART   I. 
GENERAL    CHEMISTRY. 


PART   I. 
GENERAL   CHEMISTRY. 

THE   NON-METALLIC   ELEMENTS. 

OXYGEN. 

Symbol,  O.  — Atomic  weight,  16.  —  Molecule,  02 .  —  Molecular  weight,  32. 

OXYGEN  is  by  far  the  most  important  of  all  the  elementary 
chemical  substances,  as  well  as  the  most  abundant,  both  in  the 
free  state  and  in  combination  with  other  substances. 

Free  oxygen  is  a  colorless,  tasteless,  and  odorless  gas.  It  forms 
in  the  free  state  about  one-fifth  by  measure  and  about  one-quarter 
by  weight  of  dry  air.  In  combination  with  hydrogen  as  water  it 
constitutes  eight-ninths  of  the  weight  of  the  latter  substance,  and 
in  combination  with  various  substances  it  has  been  estimated  to 
constitute  about  one-eighth  of  the  total  weight  of  the  entire  globe. 
In  the  free  or  gaseous  state  oxygen  is  necessary  to  respiration,  the 
germination  of  seeds,  the  growth  of  plants,  the  decay  of  vegetable 
substances,  and  the  commencement  of  putrefaction  in  animal 
matters.  It  is  alsa  necessary  for  the  support  of  combustion, 
though  it  is  itself  uninflammable.  Oxygen  is  the  most  magnetic  of 
all  gases ;  the  daily  variations  of  the  magnetic  needle  are  probably 
caused  by  the  effect  of  heat  in  changing  the  magnetic  properties 
of  the  gas.  Oxygen  is  only  slightly  soluble  in  water,  100  volumes 
of  water  dissolving  2.99  volumes  at  15°  C.  and  4.11  volumes  at  0°  C. 
under  the  ordinary  pressure  of  the  atmosphere. 

The  weight  of  oxygen,  as  compared  with  an  equal  volume  of 
dry  hydrogen,  or  its  specific  gravity,  is  15.96.  Pure  oxygen  may 
be  prepared  by  heating  many  of  its  compounds  —  as  manganese 
dioxide,  MnO2,  or  potassium  chlorate,  KC1O3  — in  a  closed  vessel 
to  a  temperature  sufficiently  high  to  decompose  the  compound, 

25 


20  GENERAL   CHEMISTRY. 

when  oxygen  will  be  given  off  and  may  be  collected  by  suitable 
means.  It  may  also  be  obtained  through  the  decomposition  of 
water  by  means  of  the  electric  current.  When  a  clear  solution  of 
bleaching-powder,  to  which  have  been  added  a  few  drops  of  a 
solution  of  any  cobalt  salt,  is  heated  to  about  80°  C.,  oxygen  is 
easily  and  regularly  evolved  in  considerable  quantity.  If  the 
solution  is  milky,  or  if  a  paste  made  with  bleaching-powder  and 
water  is  used  with  the  cobalt  solution,  it  is  necessary  to  add  a 
little  paraffin  oil  to  prevent  frothing.  Oxygen  was  first  prepared 
by  Priestley  in  1774  by  heating  mercuric  oxide,  HgO. 

The  process  of  union,  or  of  combination  of  oxygen  directly  with 
another  substance,  is  called  combustion  or  oxidation;  and  the 
products  of  such  combustion  are  called  Oxides.  The  weight  of  the 
products  of  combustion  is  always  equal  to  that  of  the  substance 
burned  plus  the  weight  of  the  oxygen  consumed  (combined  or 
fixed)  in  the  process.  Combustion  may  be  either  dry,  as  in  the 
burning  of  coal  in  a  grate,  or  moist,  as  in  the  combustion  (destruc- 
tion) of  coloring-matters  in  the  process  of  bleaching.  In  the 
latter  case  the  oxygen  of  the  bleaching-powder,  Ca(ClO)2,  com- 
bines with  the  coloring-matters  to  form  -eventually  dioxide  of 
carbon  or  carbonic  acid,  CO2,  and  water.  Combustion,  whether 
moist  or  dry,  is  always  attended  with  sensible  increase  of  tem- 
perature, varying  directly  with  the  rapidity  of  the  chemical  com- 
bination. Conversely,  sensible  increase  of  temperature  always 
increases  the  rapidity  of  combustion.  This  explains  the  phenome- 
non of  spontaneous  combustion.  This  only  takes  place  with  easily 
combustible  substances  and  those  which  by  their  physical  con- 
ditions expose  a  large  surface  to  the  action  of  the  oxygen  of  the 
air,  as,  for  instance,  oily  waste  or  fur.  When  a  mass  of  waste 
saturated  with  an  easily  combustible  oil  is  thrown  carelessly  in  a 
warm  place  where  it  is  exposed  to  the  air,  combination  of  the 
oxygen  with  the  oil  at  once  begins  and  heat  is  developed.  This 
in  turn  increases  the  rapidity  of  the  combination,  which  generates 
more  heat,  until  after  a  time  the  mass  becomes  hot  enough  to 
smoulder  and  then  burst  into  flame.  If,  however,  the  supply  of 
oxygen  is  limited,  as  is  the  case  when  the  waste  is  enclosed  in  a 
tight  case,  the  combustion  will  be  limited  to  the  consumption  of 
the  oxygen  within  the  case,  and  the  heat  can  never  rise  to  the 
inflaming-point.  Spontaneous  combustion  can  never  occur  in  such 
materials  loosely  exposed  or  spread  out  to  the  air,  since  in  that 


HYDROGEN.  27 


case  the  currents  of  air  and  large  radiating  surface  exposed  keep 
the  temperature  always  below  the  inflaming-point  by  carrying  oH 
the  heat  as  fast  as  it  is  generated.  Mineral  oils  have  no  tendency 
to  spontaneous  combustion,  and  when  present  in  a  mixed  oil 
greatly  lessen  the  danger  from  this  source.  When  the  proportion 
of  "mineral  oil  reaches  30  per  cent,  there  is  no  danger. 

When  sparks  from  an  electric  machine  are  passed  through 
ordinary  oxygen,  three  volumes  of  the  gas  are  condensed  into  two, 
the  gas  at  the  same  time  acquires  a  peculiar  odor,  and  has  its 
characteristic  chemical  properties  intensified  in  a  marked  degree. 
The  same  change  may  be  brought  about  in  several  other  ways. 
This  condensed  oxygen  is  called  allotropic  oxygen  or  ozone. 
When  heated  to  290°  C.  it  is  instantly  converted  into  ordinary 
oxygen.  Ozone  is  produced  in  nature  by  the  action  of  the  air  on 
gums  and  resins,  but  is  instantly  decomposed  by  contact  with 
putrescent  matters.  The  gradual  deterioration  of  rosin-sized 
paper  is  believed  to  be  due  in  part  to  the  effect  of  ozone,  formed 
by  the  action  of  the  air  upon  the  rosin  size.  Ozone  may  often  be 
detected  in  minute  quantities  in  the  air  of  the  country,  and  espe- 
cially in  the  vicinity  of  pine  forests,  but  is  almost  never  present  in 
the  air  of  thickly  settled  towns. 

It  is  a  very  energetic  bleaching  agent,  and  many  attempts  have 
been  made  to  produce  it  on  a  manufacturing  scale  for  that  pur- 
pose, but  none  have  met  with  commercial  success. 

HYDROGEN. 

Symbol,  H.-— Atomic  weight,  1.  — Molecule,  H2 .  — Molecular  weight,  2. 

Hydrogen  is  a  colorless,  tasteless,  and  odorless  gas.  As  usually 
prepared,  however,  it  always  contains  slight  traces  of  other  sub- 
stances which  impart  to  it  various  odors  more  or  less  disagreeable, 
and  characteristic  of  the  different  impurities.  It  is  the  lightest 
of  all  known  substances,  and  on  that  account  the  weight  of  the 
hydrogen  atom  is  taken  as  the  unit  or  standard  of  atomic  weights. 
A  given  volume  of  the  gas  weighs  only  0.0691  as  much  as  an 
equal  volume  of  air.  Hydrogen  is  inflammable  when  heated  in  air, 
combining  with  the  oxygen  to  produce  hydrogen  oxide,  H2O, 
water.  The  hydrogen  flame  produces  very  little  light,  being  of  a 
faint  bluish  color,  but  a  very  intense  heat. 

By  leading  hydrogen  and  oxygen  gases,  under  pressure,  through 


28  GENERAL   CHEMISTRY 


separate  tubes,  and  allowing  them  to  mix  in  the  proper  proportions 
at  t"he  point  of  ignition,  a  heat  may  be  produced  second  only  to 
that  of  the  electric  arc.  This  flame,  known  as  the  oxyhydrogen 
flame,  and  the  instrument  for  its  production  as  the  oxyhydrogen 
blowpipe,  is  made  use  of  in  the  production  of  the  calcium  light, 
which  was  the  most  powerful  light  known  previous  to  the  inven- 
tion of  the  electric  light.  In  the  production  of  the  calcium  light 
the  flame  from  the  oxyhydrogen  blowpipe  is  directed  upon  a  cyl- 
inder of  compressed  lime,  raising  the  latter  to  such  an  intense  heat 
that  it  emits  a  dazzling  white  light. 

The  oxyhydrogen  blowpipe,  or  more  often  one  in  which  air  is 
used  in  place  of  oxygen,  is  also  invaluable  to  the  plumber,  who 
employs  it  in  fusing  together  two  pieces  of  lead  int®  a  single  piece, 
the  operation  being  technically  called  lead-burning. 

Hydrogen  when  mixed  with  air  or  oxygen  in  any  quantity,  as  in 
a  flask  or  bottle,  forms  a  mixture  which  will  explode  with  terrific 
force  when  fire  is  brought  into  contact  with  it.  For  this  reason 
one  should  always  be  sure,  when  using  the  gas,  that  it  is  coming 
from  the  generator  pure,  or  unmixed  with  air,  before  applying  a 
light  to  the  stream  of  gas. 

Hydrogen  is  but  slightly  soluble  in  water.  Iron,  at  &  red  heat, 
is  penetrated  by  hydrogen.  The  gas  is  not  poisonous,  and  may  be 
breathed,  when  pure,  for  a  short  time,  without  ill  effects.  It  bos  a 
curious  action,  however,  :on  the  organs  of  speech,  raising  the  pitch 
of  the  voice  very  noticeably  after  <a  few  inspirations. 

Hydrogen  occurs  chiefly  in  combination  with  oxygen  as  water ; 
it  also  occurs  in  tfhe  larger  number  of  organic  bodies  with  oxygen 
and  carbon,  and  sometimes  nitrogen ;  and  with  carbon  alone  in  the 
mineral  oils.  It  forms  the  chief  element,  as  shown  by  the  spectro- 
scope, in  the  atmosphere  of  many  of  the  stars. 

Hydrogen  may  be  obtained  by  the  electrolysis  of  water,  or  by 
passing  steam  over  red-hot  iron,  the  oxygen  of  the  .water  unit- 
ing with  the  iron  to  make  oxide  of  iron,  and  leaving  the  hydrogen 
free.  x  ..: 

Certain  metals,  notably  sodium  and  potassium,  have  the  power 
of  decomposing  water  at  ordinary  temperatures,  with  the  formation 
of  an  oxide  of  the  metal  and  free  hydrogeiu  The  easiest  as  well 
as  least  expensive  method  of  preparing  hydrogen  in  quantity  is  by 
the  action  of  a  metal,  preferably  zinc,  on  muriatic  or  sulphuric  aoid 
diluted  with  water.  In  this  case  the  metal  takes  the  place  of 


NITEOGEN.  29 


hydrogen  in.  the  acid,  forming  chloride  or  sulphate  of  the  metal, 
and  free  H2,  as  shown  in  the  equation  — 

H2S04-f  Zii  =  Zn8O4+  H2. 

This  latter  is  the  method  used  by  plumbers  in  preparing  hydro- 
gen for  use  in  lead-burning. 

The  most  common,  as  well  as  the  most  important,  compound  of 
hydrogen  is  water,  hydrogen  oxide,  H2O. 

Water  is  a  clear  transparent  liquid,  colorless  in  small  quantities, 
but  of  a  blue  tint  in  large  masses. 

At  0°  G.  (32°  F.)  it  crystallizes  or  freezes.  At  100°  C.  (212°  F.), 
and  760  millimetres  (30  inches)  barometric  pressure,  it  is  changed 
into  an  invisible  colorless  gas  called  steam,  having  the  same  elastic- 
ity as  the  air.  Increased  pressure  raises  the  boiling-point, 'as  does 
also  the  presence  of  solids  in  solution.  Water  has  its  maximum 
density  at  4°  C.  (39£°  F.),  at  which  temperature  one  cubic  foot 
weighs  997  ounces  avoirdupois,  and  one  American  gallon  8£  Ibs. 
One  volume  of  water  will  produce  1320  volumes  of  steam  at  100°  C. 
and  760  millimetres  barometric  pressure.  Water  is  the  most  uni- 
versal solvent  known,  nearly  all  substances  being  dissolved  by  it  in 
greater  or  less  degree. 

Hydrogen  also  forms  one  other  compound  with  oxygen  which 
deserves  brief  mention ;  namely,  hydrogen  peroxide,  H2O2.  This  is 
a  liquid  heavier  than  water,  and  was  discovered  by  Thenard  in 
1818.  It  begins  to  give  off  oxygen  at  20°  C.,  arid  at  100°  C.  is  at 
once  converted  into  water,  giving  off  one-half  the  oxygen  it  con- 
tains. Half  its  oxygen  app  s  to  be  veiy  loosely  held  in  the 
molecule,  and  is  consequently  very  ready  to  unite  with  other  oxi- 
dizable  substances.  On  this  account  it  has  been  proposed  as  a 
bleaching  agent,  and  used  as  such  with  considerable  success,  but 
on  account  of  the  difficulty  and  expense  attending  its  preparation 
on  a  large  scale  it  has  never  come  into  extended  use. 

It  is  somewhat  employed  for  restoring  old  engravings. 

NITROGEN 

Symbol,  N.-— Atomic  weight,  14. —  Molecule,  N2 .  —  Molecular  weight,  28. 

Nitrogen,  discovered  in  .1772  by  Rutherford,  is  a  gas  without 
color,  taste,  or  odor.  It  is  lighter  than  air,  its  specific  gravity 
being  0.972  compared  to  air,  OP  14  compared  to  hydrogen.  Dry 
atmospheric  air  is  a  mixture  of  nitrogen  with  oxygen  in  the 


30  GENERAL   CHEMISTRY. 

proportion  of  about  four-fifths  nitrogen  and  one-fifth  oxygen  by 
volume.  Nitrogen  is  distinguished  more  for  its  negative  than  its 
positive  qualities.  It  combines  directly  with  but  few  of  the 
elements,  and,  in  these  cases  even,  its  combination  is  effected  with 
considerable  difficulty.  Nitrogen  is  uninflammable.  It  is  neither 
combustible  in  the  air,  like  hydrogen,  nor  is  it  a  supporter  of 
combustion,  like  oxygen. 

Nitrogen  may  be  easily  obtained  by  passing  air  over  red-hot 
copper,  the  oxygen  of  the  air  combining  with  the  copper  to  form 
copper  oxide,  CuO,  leaving  the  nitrogen  practically  pure.  Only 
two  compounds  of  nitrogen  are  of  sufficient  importance  to  be 
mentioned  here,  —  ammonia  and  nitric  acid.  The  former,  nitrogen 
hydride  or  ammonia,  NH3,  is  a  colorless  gas  of  strong  pungent 
odor  and  totally  irrespirable.  It  is  very  soluble  in  water  and 
alcohol,  water  at  15°  C.  dissolving  727  times  its  own  volume  of 
the  gas,  forming  the  ammonia  water  ("stronger  ammonia")  of 
commerce.  A  pressure  of  6£  atmospheres  condenses  the  gas  at 
the  ordinary  temperature  to  a  colorless  liquid,  which,  when  it  is 
allowed  to  evaporate  by  the  removal  of  the  pressure,  produces 
intense  cold.  This  property  of  anhydrous  liquid  ammonia  is 
taken  advantage  of  in  machines  for  producing  ice. 

Ammonia  is  obtained  in  the  incomplete  combustion  of  organic 
substances  containing  nitrogen  and  hydrogen.  It  is  obtained 
commercially  as  a  by-product  in  the  manufacture  of  bone  char- 
coal and  illuminating  gas.  Ammonia  is  a  strong  alkali,  and  as 
such  receives  many  useful  applications  in  the  arts. 

Oxides  of  Nitrogen. 
Nitrogen  forms  five  different  compounds  with  oxygen,  — 

NA     NA>     NA,     NA,     andNA- 

Only  the  last-mentioned,  nitric  anhydride,  N2O5,  is  of  interest  in 
this  connection.  Nitric  anhydride  is  a  brilliant  colorless  crys- 
talline solid.  When  brought  into  the  presence  of  water,  H2O,  it 
unites  with  it  to  form  nitric  acid,  HNO3,  according  to  the 
equation-  KA  +  HaO  =  2  HNO8. 

Nitric  acid,  sometimes  called  "  aqua  fortis,"  is  a  fuming  corrosive 
liquid  heavier  than  water.  It  boils  afc  85°  C.  and  freezes  at 
—  40°  C.  It  stains  the  skin  yellow  and  rapidly  destroys  its 


CAKBON.  31 


substance.  It  unites  with  alkalis  and  metallic  bases  to  form,  for 
the  most  part,  crystalline  solids  soluble  in  water,  called  nitrates. 
Potassium  nitrate,  KNO3,  is  "saltpetre,"  and  sodium  nitrate, 
NaNO3,  is  "Chili  saltpetre."  The  latter  is  brought  from  Chili  in 
large  quantities,  and  forms  the  chief  source  of  nitric  acid.  The 
acid  is  obtained  from  the  nitrate  by  distilling  the  latter  with 
sulphuric  acid.  Nitric  acid  acts  energetically  upon  most  of  the 
metals,  dissolving  them  to  form  nitrates.  It  transforms  glycerine 
into  nitro-gjyeerine  and  cellulose  into  guncotton.  Gold  and 
platinum  are  not  affected  by  pure  nitric  acid,  and  iron  is  only 
attacked  by  the  dilute  acid,  the  strong  acid  so  affecting  the 
surface  of  iron  as  to  render  it  what  is  called  passive,  and  while  in 
this  state  it.  entirely  resists  the  action  of  the  weaker  acid. 

CARBON. 

Symbol,  C.  — Atomic  Weight,  12. 

Pure  carbon  occurs  in;  nature  as  the  diamond.  In  this  form  it 
is  usually  colorless,  of  very  high  refractive  power  and  great 
brilliancy  when  cut  or  polished.  The  diamond  is  the  hardest  of 
all  known  substances  ;  it  does  not  conduct  electricity  and  is  incom- 
bustible at  the  highest  heat  attainable  by  the  blowpipe.  Heated 
in  the  voltaic  arc,  it  swells  up,  takes  the  appearance  of  coke, 
becomes  a  conductor  of  electricity,  and  is  slowly  consumed. 

Graphite  or  plumbago  is,  so  far-  as  chemists  have  been  able  to 
determine,  another  natural  form  of  pure  carbon.  Graphfte  occurs 
either  massive  or  crystallized  in  six-sided  plates,  which  have  a 
metallic  lustre.  It  is  friable  and  almost  greasy  to  the  touch  and 
leaves  a  black  mark  on  paper  —  the  mark  of  a  common  lead- 
pencil —  although  iis  ultimate  particles  are  very  hard.  It  is  an 
excellent  conductor,  of  electricity.  Graphite  is  frequently  em- 
ployed in  conjunction  with  grease  as  a  lubricator  for  machinery. 
Lignite,  stone  coal,  and  coke  are  all  more  or  less  pure  varieties  of 
carbon. 

Lampblack  is  an  artificial  variety  of  nearly  pure  carbon. 

Compounds  of  Carbon. 

Carbon  unites  with  hydrogen  to  form  a  long  series  of  com- 
pounds—  gaseous,  liquid,  and  solid  —  called  hydrocarbons,  inter- 


32  GENERAL   CHEMISTRY. 

eating  examples  of  which  are  the  gases,  naphthas,  and  oils  obtained 
from  petroleum.  These  are  all  hydrocarbons,  varying  chemically 
only  by  the  different  numbers  of  carbon  and  hydrogen  atoms 
which  go  to  form  the  molecule  in  each. 

Carbon  and   Oxygen. 

Carbon  unites  with  oxygen  in  two  different  proportions,  form- 
ing carbon  monoxide,  CO,  and  carbonic  anhydride  or  carbonic 
acid  gas,  CO2.  The  first  product  of  combustion  is  always  car- 
bonic anhydride,  but  when  this  subsequently  passes  over  red-hot 
coals  it  gives  up  a  portion  of  its  oxygen  and.  is  reduced  to  the 
monoxide.  Carbon  monoxide  is  a  colorless,  odorless  gas  about  as 
heavy  as  air.  It  is  very  poisonous  when  inhaled,  and  burns  in  the 
air  with  a  blue  flame,  forming  carbonic  anhydride.  The  same 
product  is  formed  when  the  monoxide  comes  in  contact  with 
metallic  oxides,  which  give  up  their  oxygen  with  production  of 
the  metal.  The  monoxide  thus  plays  an  important  part  in  the 
operation  of  the  blast  furnaces  used  for  smelting  iron  ore.  When 
steam  is  passed  over  red-hot  coals,  carbon  monoxide  and  hydrogen 
are  formed.  Together  they  constitute  almost  the  entire  portion  of 
the  so-called  water-gas. 

Carbonic  acid  gas  is  also  a  colorless  gas,  one  and  a  half  times 
heavier  than  air.  It  has  a  faintly  acid  taste  and  odor.  It  some- 
times collects  in  mines,  where  it  is  called  choke-damp.  It  is  formed 
during  the  fermentation  of  liquids,  and  by  its  escape  causes  the 
effervescence  noticed  in  such  liquids.  It  is  always  present  in  small 
amount  in  the  air,  and  cannot  properly  be  called  a  poison,  although 
it  becomes  injurious  if  breathed  in  excessive  amount.  Plants 
absorb  it,  retaining  the  carbon,  which  enters  into  their  structure, 
and  breathing  out  oxygen  when  in  the  sunlight.  Animals  reverse 
the  process,  absorbing  oxygen  and  eliminating  carbonic  acid  gas. 

Carbonic  anhydride  is  ul&nflammable  and  does  not  support  com- 
bustion, since  it  is  already  fully  burned.  Water  at  15°  C.,  and  at 
the  ordinary  pressure,  dissolves  its  own  volume  of  the  gas,  and  an 
additional  volume  for  eaoh  15  Ibs.  increase  of  pressure.  Water  so 
charged  forms  the  ordinary  soda-water.  By  a  pressure  of  38J  at- 
mospheres (38i  .x  15  Ibs.)  at  0°  C.,  the  gas  may  be  condensed  to  a 
colorless  liquid,  lighter  than  water,  and  may  then  be  frozen,  by  its 
own  evaporation,  to  a  snow-like  solid.  Carbon  dioxide,  as  it  is  also 


CAltBON.  33 


called,  is  a  product  of  the  wet  or  dry  combustion  of  all  bodies  con- 
taining carbon.  It  is  evolved  in  large  quantities  from  the  kilns  in 
which  limestone  is  burned,  and  from  the  top  of  the  limestone 
towers  used  in  making  sulphite  liquor. 

In  presence  of  water  carbonic  anhydride  forms  the  true  car- 
bonic acid,  which  unites  with  bases  to  form  carbonates.  Almost 
all  the  carbonates,  except  those  of  potassium,  sodium,  and  ammo- 
nium, are  nearly  or  quite  insoluble  in  water,  although  rather  soluble 
in  water  containing  carbonic  acid.  Marble  is  nearly  pure  carbonate 
of  calcium.  All  carbonates  give  off  their  carbonic  acid  with  effer- 
vescence, on  the  addition  of  one  of  the  stronger  acids. 

Combustion.  — All  combustion,  in  the  ordinary  sense  of  the  word, 
as  already  noted  under  Oxygen,  is  a  process  of  combination  with 
oxygen.  In  the  pure  gas  such  combination,  once  started,  proceeds 
with  uncontrollable  energy  until  the  combustible  body  is  consumed ; 
but  in  ordinary  cases  the  supply  of  oxygen  is  drawn  from  the 
atmosphere,  where  one-quarter  by  weight  of  oxygen  is  diluted  with 
three-quarters  of  inert  nitrogen.  The  following  reactions  serve  to 
illustrate  the  more  typical  cases  of  combustion,  and  indicate  th 
resulting  products :  — 

Combustion  of  hydrogen    .     .     .  2  H2  +  02  =  2  H2O 

"          of  carbon  (charcoal)  C  +  O2  =  C02 

"          of  marsh  gas       .     .  CH4  +2O2  =  C02  +  2H2O 

"          of  alcohol.     .     .     .  C2H5OH-f  3O2  =  2CO2  + 3  H20 

"          of  sulphur      .     .     .  S2  -f-  2  O2  =  2  SO2 

"          of  phosphorus     .     .  P4  +  5  O2  =  2  P205 

The  ordinary  combustibles,  like  coal,  wood,  petroleum,  and  illu- 
minating gas,  are  compounds  of  carbon  and  hydrogen,  and  form  by 
their  burning  carbonic  acid  gas  and  water.  The  light  and  heat 
developed  during  combustion  are  due  to  the  rushing  together  of 
the  atoms  under  the  attractive  force  of  chemical  affinity.  The 
amount  of  heat  developed  varies  greatly  with  different  combusti- 
bles, and  depends  upon  the  kind  of  atoms  composing  their  molecules, 
and  the  extent  to  which  the  affinities  of  these  atoms  are  already 
satisfied.  The  number  of  heat  units  developed  by  the  combus- 
tion of  one  kilogramme  of  several  different  substances  is  given 
on  the  following  page :  — 


84  GENERAL   CHEMISTRY. 

Hydrogen »•  * . .  i .  v  •:  *,  . .  34462 

Alcohol  .  .  .  .  .  ...  r.  ...  7184 

Sulphur  .  .  .  .  :.  &  :.,.  :.  .  .  2221 

Charcoal  .  ../.,.  ,  ,  .  .  8080 

Pry  wood  .  .  ,  .  ...  .  .  3654 

Soft  coal  .  .  .  .  .  .  .  .  .  7500 

Gas  coke  .........  8047 

If  a  flame  like  that  of  an  ordinary  candle  is  inspected  closely, 
the  existence  of  three  distinct  zones,  as  shown  in  Figure  1,  may 
be  detected.  The  innermost,  dark  zone,  consists  of 
gas  formed  by  heat  from  the  melted  wax  drawn  up 
by  the  capillary  action  of  the  wick.  The  two  outer 
zones  shut  off  the  inner  one  from  the  oxygen  of  the 
air,  and  there  is  consequently  no  combustion  within 
this  zone.  The  middle  zone  is  the  one  from  which 
most  of  the  light  is  derived.  There  is  here  not  suffi- 
cient air  for  complete  combustion,  and  the  minute 
particles  of  carbon  are  rendered  incandescent  by  the 
heat.  The  flame  at  this  point  is  a  reducing  one, 
because  the  white-hot  carbon  and  partially  burned 
gases  possess  so  strong  an  affinity  for  oxygen  that 
Fl0-.1'  many  metallic  oxides  give  up  their  oxygen  and  are 
reduced  to  the  metal  if  this  portion  of  the  flame  is  brought  to  bear 
upon  them.  The  carbon  and  gases  are  completely  burned  to  CO2 
and  H2O  in  the  outer  zone,  in  which,  of  course,  an  excess  of  oxygen 
is  present ;  and  tl*e  action  of  the  flame  at  this  point  is  an  oxidizing 
one,  since  conditions  are  favorable  for  the  oxidation  of  a  metarl 
brought  within  it. 

Carbon  unites  with  both  oxygen  and  hydrogen  to  f 6rm  a  large 
class  of  organic  substances  called  carbohydrates,  of  which  sugar, 
CwHaOii,  starch,  and  cellulose  (CH10O5)W,  are  notable  examples. 
Many  of  these  substances,  as,  for  instance,  starch  and  cellulose, 
have  the  same  number  of  the  elementary  atoms  in  the  molecule,  so 
that  their  percentage  composition,  or  the  proportion  of  O,  H,  and  O, 
is  the  same  in  each.  In  these  cases  the  different  character  of  the 
substances  is  supposed  to  bo  due  to  a  different  arrangement  of  the 
several  atoms  in  the  individual  molecule.. 

Many  of  the  carbohydrates  are  valuable  food  substances,  being 
burned  in  the  system  by  means  of  the  oxygen  inhaled,  and  furnish- 
ing fuel,  so  to  speak,  for  the  fires  of  life.  Any  superabundance 


SULPHUR.  85 

above  what  may  be  required  for  keeping  up  the  animal  heat  and 
energy  is  either  voided  unchanged  or  is  transformed  into  fat  and 
stored  as  such  in  the  body,  according  to  the  vigor  of  the  individual 
system.  The  number  of  the  various  compounds  in  the  organic  world 
into  which  carbon  enters  is  almost  infinite,  and  the  study  of  the 
carbon  compounds,  or  organic  chemistr}',  forms  a  science  in  itself. 
Probably  no  other  element,  if  we  except  oxygen,  takes  part  in 
the  formation  of  such  a  variety  of  compounds  of  the  highest  use  to 
man  as  carbon. 

Carbon  and  Nitrogeh. 

When  air  is  passed  over  potassium  carbonate  mixed  with  char- 
coal, and  contained  in  a  red-hot  tube,  the  nitrogen  of  the  air  unites 
\vith  carbon  to  produce  a  colorless  and  extremely  poisonous  gas, 
called  cyanogen,  C2N2,  which  has  the  odor  of  peach  blossoms  or 
bitter  almonds.  Cyanogen  is  1.8  times  as  heavy  as  air.  It  is 
easily  condensed  by  cold  and  pressure  into  a  colorless  liquid. 
Water  dissolves  four  times  its  volume  of  the  gas.  When  heated 
in  the  air  cyanogen  burns  with  a  beautiful  pink  flame,  producing 
carbon  dioxide  and  free  nitrogen.  Cyanogen  unites  directly  with 
hydrogen  to  form  cyanhydric  or  "Prussic"  acid,  CNH,  a  colorless 
transparent  liquid  most  intensely  poisonous.  When  inhaled,  even 
in  very  minute  quantities,  it  produces  headache,  ^giddiness,  etc. 
The  hydrogen  in  prussic  acid  may  be  replaced  by  metals  to  form 
cyanides.  Cyanogen,  under  certain  conditions,  may  be  made  to 
unite  with  iron  and  potassium  to  form  f errocyanide  and  f en-icy anide 
of  potassium. 

The  ferricyanide  of  potassium  is  red,  and  is  commonly  known 
as  red  prussiate  of  potash.  Its  solutions,  when  mixed  with  those 
of  ferrous  salts  (see  Iron),  yield  a  blue  precipitate.  Ferrocyanide 
of  potassium,  or  yellow  prussiate  of  potash,  occurs  in  beautiful 
yellow  crystals.  It  gives  a  white  precipitate  with  ferrous  salts, 
which  turns  blue  on  exposure  to  the  air.  With  ferric  salts,  which 
contain  more  oxygen,  the  precipitate  is  the  ordinary  Prussian 
blue. 

SULPHUR. 

Symbol,  S.  —  Atomic  weight,  32.  —  Molecule,  S2 .  —  Molecular  weight,  64. 

Sulphur  is  a  pale-yellow,  brittle  solid  of  specific  gravity  2.045. 
It  occurs  native  in  Sicily,  and  on  the  shores  of  the  Mediterranean 


86  GENERAL   CHEMISTRY. 

Sea,  in  Japan,  and  in  Utah,  and  some  other  parts  of  the  western 
portions  of  the  United  States.  The  principal  commercial  source  of 
sulphur  is  Sicily,  though  considerable  quantities  reach  the  Pacific 
coast  from  Japan,  and  an  occasional  cargo  of  Japanese  sulphur  may 
be  found  in  New  York.  The  deposits  in  our  own  country,  although 
\eryextensive  and  of  high-grade  ore,  remain  at  present  in  an  unde- 
veloped condition.  In  Sicily  the  sulphur  is  found  mixed  with 
earth,  and  to  prepare  it  for  export  large  heaps  of  the  sulphur-bear- 
ing earth  are  formed  around  a  central  opening  and  covered  with 
turf,  air  channels  being  left  near  the  bottom  of  the  heaps.  Some 
brushwood  is  laid  at  the  bottom  in  building  the  heap.  When  the 
mound  is  finished  the  brushwood  is  fired,  and  the  heat  from  this 
melts  a  portion  of  the  sulphur,  which  runs  toward  the  central  hole, 
and  there  accumulates,  to  be  drawn  off  from  time  to  time  into  pans, 
where  it  is  allowed  to  cool.  Only  a  small  quantity  of  wood  is  used 
to  start  the  heap,  since  as  soon  as  the  sulphur  begins  to  melt  a 
portion  of  it  is  ignited  and  serves  to  heat  the  pile.  The  amount  of 
air  admitted  through  the  air  channels  is  carefully  regulated  so  as 
only  to  allow  enough  sulphur  to  be  burned  to  keep  up  the  very 
moderate  heat  required. 

In  England  considerable  quantities  of  sulphur  are  now  being 
recovered  by  the  Chance  process,  in  an  almost  chemically  pure 
state,  as  a  by-product  in  the  Leblanc  process  of  soda  manufacture* 
Chance  treats  the  waste  sulphide  of  calcium  with  carbonic  acid  to 
expel  the  sulphur  as  sulphuretted  hydrogen,  H2S.  By  carefully 
regulating  the  supply  of  air  this  is  then  burned  in  accordance  with 
the  reaction  — 

H2S  +  O  =  H20  +  S 

into  wateiy  vapor  and  sulphur. 

Sulphur  melts  at  114°  C.  (238°  F.)  to  a  thin,  amber-colored  fluid. 
On  further  heating,  the  liquid  thickens  and  turns  dark,  until  at 
about  240°  C.  it  is  very  nearly  black,  and  so  thick  and  tenacious 
that  the  vessel  containing  it  may  be  inverted  without  the  sulphur 
running  out.  At  a  still  higher  temperature  it  again  forms  a  thin 
liquid,  and  at  446°  C.  boils  and  gives  off  vapors  or  sublimes.  This 
sulphur  vapor,  when  condensed  or  sublimed,  forms  a  fine  crystalline 
powder,  known  in  pharmacy  as  "  Flower  "  or  Flowers  of  Sulphur. 

Native  sulphur  is  found  crystallized  in  the  form  of  octahedrons, 
and  when  crystallized  from  solution  in  carbon  disulphide,  sulphur 
always  takes  this  form.  When,  however,  sulphur  is  melted  and 


SULPHUR.  87 


allowed  to  cool,  it  crystallizes  in  the  form  of  oblique  prisms,  having 
a  specific  gravity  of  1.98. 

A  third  modification  of  sulphur  appears  when  that  substance,  at 
a  temperature  of  about  250°  C.,  or  in  the  second,,  liquid  stage,  is 
poured  slowly  into  water.  It  then  appears  as  an  elastic  ductile 
solid,  soft  and  resembling  in  a  marked  degree  crude,  caoutchouc  or 
rubber.  On  exposure  to  the  air,  however,  this  modified  sulphur 
soon  loses  its  amorphous  form,  and  returns  to  the  ordinary  pris- 
matic variety. 

Sulphur  is  insoluble  in  water,  and  only  very  slightly  soluble  in 
alcohol.  It  is  somewhat  more  soluble  in  ether  and  the  essential 
oils  generally,  and  in  petroleum  naphtha.  It  is  abundantly  soluble 
in  carbon  disulphide,  CS2;  in  sulphur  dichloride,  S2C12 ;  benzene, 
coal-tar  naphtha,  C6H6;  and  in  boiling  turpentine  spirit,  C10H16. 

Sulphur  burns  readily  in  the  air,  with*  a  beautiful  blue  flame, 
producing  sulphur  dioxide,  SO2,  sulphurous  acid  gas. 

Four  qualities  of  sulphur  are  recognized  by  the  trade.  "  Firsts  " 
consist  of  large,  shining  pieces  of  amber  color ;  "seconds  "  are  not 
so  shining,  but  are  still  purely  yellow  ,r"  thirds  "  are  of  a  dirtier 
color,  often  inclining  to  red  or  brown,  and  both  these-latter  qualities 
contain  much  powder.  "Recovered"  sulphur,  so  called  from  its 
method  of  preparation  from  alkali  waste,  is  equal  in  color  to  firsts 
and  contains  only  a  trace  of  impurity.  Unlike  the  other  grades, 
which  are  shipped  in  bulk,  recovered  sulphur  is  usually  shipped  in 
bags.  The  total  ash  of  commercial  Sicily  sulphur  is  rarely  over 
2  per  cent.,  and  often  only  0.5  per  cent. 

Compounds  of  Sulphur. 

SULPHIDES. 

Sulphur  unites  directly  with  most  of  the  metals,  when  heated 
with  them,  to  form  sulphides.  Copper,  for  esa&nple,  when  heatml 
to  redness  in  vapor  of  sulphur,  unites  with  the  latter  to  form 
copper  sulphide,  CuS.  Many  of  the  sulphides  of  the  metals  are 
found  in  nature,  and  sometimes,  as  in  the  case  of  lead  sulphide, 
galena,  PbS,  and  mercury  sulphide,  cinnabar,  HgS,  form  the  most 
valuable  ores  of  the  metals.  Iron  pyrites,  FeS2,  and  copper  pyrites, 
FeCuSg,  are  valuable  minerals,  both  for  the  sulphur  they  contain 
end  alfco  for  their  metal.  Both  minerals  occur  as  golden-yellow 


88  GENERAL   CHEMISTRY. 

masses,  or  crystalline  grains,  so  often  mistaken  for  gold  that  they 
have  received  the  name  of  "  Fool's  gold."  By  roasting  iron  pyrites 
and  many  other  native  sulphides,  with  free  access  of  air,  all  the 
sulphur  may  be  burned  out  of  the  mineral,  going  off  as  sulphurous 
acid  gas,  SO2,  which  may  be  utilized  for  various  purposes,  as  the 
making  of  "  sulphite  liquors  "  for  the  manufacture  of  sulphite  pulp, 
etc.  Iron  pyrites,  often  containing  more  or  less  copper,  is  the 
sulphide  usually  chosen  for  this  purpose  on  account  of  its  larger 
content  of  sulphur  than  many  others,  and  of  the  ease  and  complete- 
ness with  which  the  sulphur  may  be  burned  out  in  a  properly  con- 
structed furnace. 

Most  of  the  native  sulphides  are  insoluble  in  dilute  acids.  When, 
however,  artificially  prepared  sulphides,  as  sulphide  of  iron,  FeS, 
are  treated  with  dilute  hydrochloric  or  sulphuric  acid,  HC1,  or 
H2SO4,  the  metal  is  dissolved  to  form  a  metallic  chloride  or  sul- 
phate, while  the  sulphur  of  the  sulphide  and  the  hydrogen  of  the 
acid  are  simultaneously  freed  from  the  former  combinations,  and 
unite  to  form  hydrogen  sulphide,  sulphuretted  hydrogen,  U2S. 
Sulphur  and  hydrogen  combine  directly  only  when  both  are  in 
what  is  called  the  nascent  condition ;  that  is,  at  the  instant  of  their 
liberation  from  some  previous  combination. 

Nearly  all  the  sulphur  which  abroad  enters  into  the  manufacture 
of  sulphuric  acid  is  derived  from  iron  pyrites,  containing  more  or 
less  copper,  and  usually  a  small  amount  of  arsenic.  Pyrites  furnish 
the  cheapest  source  of  sulphur,  but  require  for  their  burning  a 
much  more  elaborate  andi  expensive  plant  than  the  element  itself, 
and  a  considerable  quantity  of  fine  brown  dust  is  carried  along  with 
the  gas.  For  these  reasons  sulphur  has  usually  :been  preferred  by 
sulphite  mills,  although  in  a  few  instances  pyrites  have  been  intro- 
duced. The  content  of  sulphur  in  the  different  ores  varies  from  27 
to  about  50  per  cent.,  good  ores  usually  carrying  about  45  per  cent. 

Hydrogen  Sulphide,  H2S,  is  a  colorless  gas  of  an  extremely  of- 
fensive odor.  It  possesses  narcotic  properties.  It  is  somewhat 
heavier  than  air.  Water  dissolves,  at  the  ordinary  temperature,  a 
little  more  than  three  times  its  volume  of  the  gas.  By  a  pressure 
of  17  atmospheres  H2S  may  be  condensed  to  a  liquid.  It  is  usually 
formed  in  the  decay  or  putrefaction  of  organic  substances  which 
contain  sulphur,  either  in  their  own  composition  or  that  of  a  com- 
pound of  sulphur  mixed  with  them.  This  fact  explains  the  fetid 
odor  sometimes  noticed  in  sulphite  pulp,  or  soda  pulp,  which  .has 


SULPHUR.  39 


been  allowed  to  remain  in  the  drainers  or  other  unventilated  place 
for  some  time  before  it  is  properly  washed.  In  both  cases  the 
liquors  left  in  the  pulp  contain  compounds  of  sulphur,  and  the 
commencing  decay  of  organic  substances  in  the  pulp,  or  of  the  pulp 
itself,  begets  a  change  in  the  sulphur  compound,  which  results 
in  the  production  of  H2S.  The  darkened  color  of  such  ill-smelling 
pulp  may  be  accounted  for  in  two  ways,  either  by  the  presence  in  the 
solution  of  traces  of  metals  which  would  be  transformed  into  black 
sulphides  by  the  H2S  formed,  or  the  presence  of  organic  matters  in 
the  pulp,  other  than  cellulose,  may  determine  the  decomposition 
of  a  portion  of  the  H2S  formed  with  the  production  of  a  dark  color 
by  the  precipitation  of  free  sulphur.  Pure  cellulose  is  not  dark- 
ened by  H2S,  but  if  left  in  contact  with  H2S,  in  the  presence  of  air, 
for  any  considerable  time,  sulphur  is  precipitated  in  it  by  the 
decomposition  of  the  H2S,  and  it  takes  on  a  more  or  less  dark  color. 
Hydrogen  sulphide,  or  sulphuretted  hydrogen,  burns  with  a  blue 
flame  to  form  water  and  sulphurous  acid  gas.  It  forms  one  of 
the  most  valuable  reagents  to  the  analyst,  as  by  its  aid  he  is  able  to 
separate  the  common  metals  from  all  other  substances. 


Sulphur  and   Oxygen. 

Sulphur  unites  with  oxygen  in  a  great  variety  of  proportions  to 
form  oxides  of  sulphur,  or,  as  they  are  termed,  sulphur  anhydrides, 
which  in  turn  unite  with  the  elements  of  water  to  form  sulphur 
acids,  or  with  metallic  oxides  to  form  sulphur  salts.  Hie  follow- 
ing is  a  list/ of  the  various  t>xddes  of  sulphur,  with  their -correspond- 
ing acids :  — 

SO    -f  H20  =  H2SO.,  ....  Hyposulphurous  acid. 

502  +  H,0  =  H2SO3  ....  Sulphurous  acid. 
S2O2  -I-  H2O  =  H2S2O3  .....  Thiosulphuric  acid.1 

503  +  H2O  =  H2S04  .     .     .     .  Sulphuric  acid. 
S ,04  -f  H2O  =  H2S2O5  .     .     .     .  Di-thionic  acid. 
S304  +  H2O  =  H2S3O5  ....  Tri-thionic  acid. 
S404 -f  H20  =  H2S4O5  ....  Tetra-thionic  acid. 
S504  -f  H2O  =  H2S5O5         .     .     .  Penta-thionic  acid. 

1  Often  improperly  called  hyposulphurous  acid. 


40  GENERAL   CHEMISTRY. 

Only  the  first  four  of  these  are  of  common  occurrence  or  use  in 
the  arts.  These  we  will  consider  in  the  natural  order  of  their 
manufacture  from  sulphur.  When  sulphur  is  burned  with  free 
access  of  air,  it  combines  with  oxygen,  as  we  have  already  said,  to 
form  sulphur  dioxide,  SO2,  called  sulphurous  anhydride,  or  sul- 
phurous acid  gas.  This  is  the  starting-point  for  the  manufacture 
of  all  the  oxygen  compounds  of  sulphur.  Either  sulphur  may  be 
used  or  pyrites,  which  gives  up  its  sulphur  as  SO2  on  heating  in  air. 
When  the  latter  is  employed  as  the  source  of  sulphur,  a  furnace  for 
burning  it  must  be  used,  in  which  more  or  less  elaborate  mechanical 
appliances  are  necessary  to  facilitate  the  handling  of  the  ore  and 
the  removal  of  the  burned  cinder,  called  "  Blue  Billy."  In  the 
burning  of  sulphur  only  the  simplest  appliances  are  necessary.  A 
furnace  as  satisfactory  as  any  for  this  purpose  consists  simply  of  a 
cast-iron  retort,  with  a  flat  bottom  and  arched  top,  one  end  being 
open,  and  a  pipe  leading  from  the  crown  of  the  arch  near  the 
closed  end  for  the  escape  of  the  SO2  formed.  The  front,  or  open 
end,  is  fitted  with  a  sliding  iron  door,  which  may  be  raised  or 
lowered  to  regulate  the  admission  of  air.  The  sulphur  is  fed  in 
through  this  door  on  to  the  bottom  of  the  retort,  and  once  ignited 
needs  no  other  fuel  to  keep  it  burning.  Water  is  allowed  to 
trickle  continuously  upon  the  top  of  the  retort  in  order  to  keep 
the  heat  below  the  boiling-point  of  sulphur,  and  prevent  its  *'  sub- 
liming," or  going  away  in  vapor  without  burning,  as  in  this  event 
it  would  be  deposited  in  the  cooler  portions  of  the  pipes,  to  cause 
trouble  by  clogging.  In  the  manufacture  of  "  sulphite  liquor  "  for 
reducing  wood,  the  gas  is  usually  led  through  tanks  containing 
milk  of  lime  or  magnesia,  as  will  be  described  under  the  Sulphite 
Pulp  Process,  which  see. 

Sulphurous  acid  gas,  SO2 ,  properly  called  sulphurous  anhydride 
("  without  water  "),  is  a  colorless,  pungent,  suffocating  gas,  of  a 
specific  gravity,  compared  with  air,  of  2.21.  So  long  as  sulphurous 
anhydride  is  kept  from  contact  with  moisture,  it  remains  an  inert 
gas,  having  no  effect  upon  metals  or  other  dry  substances  with 
which  it  may  come  in  contact. 

Sulphurous  anhydride  may  be  readily  prepared  for  laboratory 
experiments  by  heating  metallic  copper  with  strong  sulphuric  acid. 
The  reaction  is  represented  by  the  equation  — 

Cu  +  2  H,SO4  =  CuSO4  -f  H2O  -f-  S02. 


THE  SULPHITES.  41 


Water  at  0°  C.  will  absorb  79.8  times  its  volume  of  SO2,  and  39.4 
times  its  own  volume  at  20°  C.  Sulphurous  anhydride  is  con- 
densed into  a  liquid  by  a  temperature  of  —  17.8°  C.,  and  by  increased 
pressure  it  may  be  liquefied  at  considerably  higher  temperatures. 
Liquid  SO2  may  be  obtained  in  syphons  similar  to  those  in  which 
Seltzer  and  other  carbonated  waters  are  sold. 

Sulphurous  anhydride  combines  with  one  molecule  of  water  to 
form  sulphurous  acid,  H2SO3,  as  before  shown  on  page  39,  and  then 
becomes  an  extremely  active  substance.  It  attacks  and  rapidly 
corrodes  most  of  the  metals,  dissolving  or  combining  with  them  to 
form  sulphites.  Copper,  zinc,  tin,  aluminum,  and  iron  are  rapidly 
eaten  away  by  solutions  of  sulphurous  acid.  Lead,  however,  and 
alloys  of  that  metal  with  antimony  resist  its  action  almost  entirely. 
Certain  alloys,  in  which  copper  forms  the  greater  part  of  the  metal, 
resist  the  action  of  sulphurous  acid  to  a  very  considerable  extent. 
All  of  them,  however,  yield  to  the  action  of  the  acid  more  or  less 
rapidly. 

Sulphurous  acid  is  able  to  decompose  the  oxides,  hydrates,  and 
carbonates  of  the  alkali  metals,  and  metals  of  the  alkaline  earths 
forming  sulphites  of  the  metals,  and  water,  in  the  case  of  the  oxides 
and  hydrates  ;  and  sulphites  of  the  metals,  water  and  carbonic  acid 
in  case  of  the  carbonates,  thus  :  — 

No/)     -f  H2SO3  =  Na2SO3  -f  H2O  ; 
2NaHO    -f  H2S03  =  Na2S03-f-2H2Oj 
Na*CO3  +  H2SO3  =  Na2S03  +  H2O  +  CO2  ; 
CaO       4-H2S03  =  CaS03  +  H,0  ; 
CaC08   -|-HiSO3  =  CaS03  +  H20  -f  C02. 


Bisulphites,  preferably  called  Acid  Sulphites.  —  Sulphurous 
acid,  HjSOjj,  like  all  the  oxygen  acids  of  sulphur,  is  a  bibasic  acid; 
that  is,  it  contains  two  atoms  of  basic  hydrogen,  or  hydrogen  so  situ- 
ated with  reference  to  the  other  atoms  in  the  molecule  that  it  may 
be  replaced  by  an  equal  number  of  atoms  of  a  univalent  alkali  metal 
as  sodium,  or  by  a  single  atom  of  a  bivalent  alkaline  earth  metal,  as 
calcium  or  magnesium.  There  are,  in  consequence,  two  series  of 
sulphites,  the  neutral  or  normal,  or  monosulphites,  mentioned  in 
the  preceding  paragraph,  in  which  compounds  both  the  hydrogen 
atoms  are  replaced  by  a  metal,  and  the  bisulphites,  or  acid  sulphites, 
in  which  only  one  of  the  hydrogen  atoms  in  the  molecule  of  acid  is 


42  GENERAL   CHEMISTRY. 

replaced  by  a  metal.  The  bisulphites  therefore  retain  much  more 
of  the  acid  character  than  do  the  normal  sulphites.  This  difference 
in  the  structure  of  the  two  molecules  may  be  shown  thus  :  — 

Normal  sodium  sulphite.  Sodium  bisulphite. 

Ka-0\  H-0X 

>=o  ;s=o 

Na-O/  Na.-O/ 

Normal  calcium  sulphite.  Calcium  bisulphite. 

/Ox  H-0X 

ca         =o  =o 


Sulphurous  acid. 

H~°  ° 


\ 


H-CK  R-0/ 

The  contracted  or  empirical  formula  of  the  bisulphites  named  is 
for  sodium  bisulphite,  HNaSO3;  for  calcium  bisulphite,  H2CaS2O6. 
It  will  be  noticed  that,  because  calcium  is  a  bivalent  metal,  two 
molecules  of  sulphurous  acid  unite  with  one  atom  of  calcium  in 
forming  the  bisulphite. 

The  bisulphites  are  formed  when  only  sufficient  of  the  base  is 
added  to  a  solution  of  sulphurous  acid  to  half  neutralize  the  acid, 
or  more  commonly  in  practice,  as  in  the  manufacture  of  sulphite 
liquors,  by  first  bringing  sufficient  acid  into  contact  with  the  base 
to  form  the  normal  sulphite,  and  then  continuing  the  addition  of 
sulphurous  acid  until  the  normal  sulphite  is  converted  into  the 
bisulphite.  They  may  .also  be  formed  by  adding  to  the  normal 
sulphite  enough  of  a  stronger  acid  than  sulphurous  to  displace  -one- 
half  the  sulphurous  acid,  thus  :  — 


Sulphuric  acid  +  "  =  Sod™  «"*"•>• 

H£O<  +  2Na2SOs   =      Na2S04     4-    2HNaSOs. 

A  similar  reaction  takes  place,  to  some  extent,  in  sulphite 
digesters,  when,  during  the  boiling  operation,  a  portion  of  the 
sulphurous  acid  is  oxidized  to  sulphuric  acid  ;  although,  if  the 
sulphite  liquor  contains  only  bisulphite  at  the  start,  the  sulphurous 
acid  displaced  appears  as  free  sulphurous  acid,  and  increases  the 
gas  pressure. 

The  acid  sulphites  (bisulphites)  of  the  alkaline  earth  metals  are 
what  are  called  loose  or  unstable  chemical  compounds,  being  easily 


THE  SULPHITES.  43 


broken  up  or  decomposed  into  the  neutral  salt  and  free  acid  by 
heat  alone;  the  acid  being  volatilized.  Acid  sulphite  of  magne- 
sium is  less  easily  decomposed  than  the  corresponding  calcium  salt, 
but  both  are  so  unstable  that  their  solutions  cannot  be  evaporated 
without  decomposing  the  salt.  Neither  of  these  salts  has  been 
isolated,  and  indeed  many  good  authorities  hold  the  opinion  that 
acid  sulphites  of  the  alkaline  earth  metals  do  not  exist,  the  so-called 
bisulphite  solutions  of  these  bases  being  simply  solutions  of  the 
neutral  sulphite  in  aqueous  sulphurous  acid.  Certain  facts  in  our 
own  experience  with  these  solutions,  however,  make  us  strongly 
of  the  opinion  that  these  salts  are  formed  and  do  exist  in  the  so- 
called  bisulphite  solutions.  Certainly  there  is  no  theoretical  reason 
why  they  may  not  be  formed. 

The  acid  sulphites  of  the  alkali  metals  are  definite  compounds, 
and  can  be  crystallized  from  their  solutions.  Both  the  neutral  and 
acid  sulphites  of  the  alkali  metals  are  very  soluble  in  water. 
Neutral  sulphite  of  magnesia  is  much  less  soluble,  while  that  of 
calcium  is  nearly  insoluble.  Neutral  sulphite  of  magnesium  sepa- 
rates from  solution  in  coarse,  sandy  crystals,  while  that  of  calcium 
forms  a  fine,  granular  precipitate  when  SO2  gas  is  passed  into  lime- 
water.  It  often  forms  coral-like  crusts  on  the  containing  vessels, 
and,  when  precipitated  by  heat  from  the  solution  of  the  acid  sul- 
phite, often  concretes  in  hard,  stony  masses.  It  frequently  appears 
in  the  bottom  and  on  the  sides  of  .digesters  used  for  "  cooking " 
wood  with  bisulphite  of  lime,  sometimes  forming  a  scale  an  inch  or 
more  in  thickness. 

All  the  bi-  or  acid  sulphites  appear  to  be  soluble  in  water.  The 
addition  of  any  of  the  stronger  acids  to  a  sulphite  causes  the  libera- 
tion of  SO2,  often  with  effervescence.  The  acid  sulphites  form 
soluble,  and  many  of  them  crystallizable,  compounds  with  certain 
organic  substances  called  aldehydes  and  ketones,  and  to  this  fact  is 
probably  due,  in  part  at  least,  their  efncienc}r  in  reducing  wood  to 
fibre. 

Sulphurous  acid,  both  free  and  in  combination,  is  very  ready  to 
take  on  more  oxygen  and  be  changed  into  sulphuric  acid.  Hence 
it  is  called  a  reducing  agent,  since  it  can  reduce  certain  other  com- 
pounds from  a  higher  to  a  lower  state  of  oxidation,  being  itself,  at 
the  same  time,  oxidized.  This  property  .gives  it  its  value  as  an 
antiohlor,  it  being  more  easily  oxidized  by  the  "  bleach  "  than  is  the 
fibre. 


44  GENERAL   CHEMISTRY. 

This  reducing  action  is  of  first  importance  in  the  sulphite  process 
for  making  pulp,  since,  on  account  of  it,  any  oxidation  and  con- 
sequent weakening  of  the  fibre  is  prevented,  while  the  incrusting 
matters  of  the  wood  are  so  little  changed  by  the  process  of  solution 
that  there  is  good  reason  to  believe  that  they  may  be  made  to  yield 
valuable  by-products. 

Sulphurous  acid  also  possesses  marked  bleaching  power,  which 
depends  on  the  fact  that  the  acid  forms  colorless  compounds  with 
the  coloring-matter.  These  compounds  may  often  be  broken  up, 
and  the  color  restored,  by  treatment  with  alkali.  The  sulphurous 
acid  bleach  is  not  a  permanent  one,  like  that  obtained  by  the  use 
of  hypochlorites,  which  destroy  the  coloring-matter.  The  acift  is 
used  for  bleaching  wool  and  straw.  It  also  gives  a  fictitious  .color 
to  sulphite  pulp.  Such  pulp,  after  washing,  is  often  as  white  as  it 
is  after  bleaching  with  bleaching-powder,  although  this  first  color 
is  not  very  permanent. 

The  moist  gas  and  also  the  sulphites  and  bisulphites  are  very 
destructive  to  the  lower  forms  of  life,  preventing  fermentation  and 
destroying  disease  germs.  They  are  much  employed  as  disinfec- 
tants. 

Hyposulphurous  Acid,  H2SO2  .  —  When  aqueous  sulphurous 
acid  is  poured  upon  zinc,  best  in  the  shape  of  clippings  or  zinc 
dust,  the  metal  dissolves,  but  no  hydrogen  is  evolved.  The  nascent 
hydrogen  formed  combines  at  once  with  an  atom  of  oxygen,  which 
it  takes  from  the  molecule  of  sulphurous  acid,  with  formation  of 
hyposulphurous  acid  and  water.  Thus  — 

H2SO3  +  M^  TI3SO2  +  HjjO. 

When  the  zinc  is  added  to  a  solution  of  a  bisulphite,  as,  for 
instance,  bisulphite  of  soda,  the  reaction  is  as  follows  :  — 


3  NaHS03  +  Zn  =  NaHSO2  (^ffigjj116)  +  NaJSO,  +  ZnSO8  -f  H20. 


Hyposulphurous  acid  has  never  been  isolated.  It  is  produced  in 
the  decomposition  of  sulphurous  acid  by  the  electric  current,  but 
is  Auch  an  unstable  compound  that  it  reoxidizes  to  sulphurous  acid 
almost  immediately.  All  its  salts  are  very  unstable,  contact  with 
the  air  very  rapidly  changing  them,  through  absorption  of  oxygen, 
to  the  acid  sulphites.  The  hyposulphites  are  extremely  power- 
ful reducing  agents  ;  that  is,  they  act  powerfully  in  withdrawing 


SULPHURIC  ACID.  45 


oxygen  from  other  compounds  of  this  element,  reducing  them  to  a 
lower  state  of  oxidation.  They  are  even  capable  of  reducing  indigo 
to  the  soluble  and  colorless  form,  and  have  been  commercially 
applied  for  this  purpose. 

Calcium  hyposulphite  is  the  salt  usually  chosen  for  this  purpose 
on  account  of  the  comparative  ease  of  its  preparation,  and  because 
it  is  the  most  stable  in  solution  of  these  compounds.  Only  one  of 
the  hyposulphites  has  been  obtained  in  the  solid,  or  crystallized, 
form  ;  namely,  sodium  hyposulphite.  This  salt  may,  by  the  exer- 
cise of  great  care  in  the  manipulation  of  a  somewhat  lengthy  proc- 
ess, be  crystallized  from  its  alcoholic  solution,  and  may  be  pre- 
served for  some  time,  if  carefully  kept  from  contact  with  the  air. 

Th  iosul  phu  ric  Acid,  H^Gg  .  —  This  acid  is,  like  the  preceding, 
not  known  in  the  free  state  ;  any  attempt  to  separate  it  from  one 
of  its  salts  resulting  in  the  breaking  up  of  the  acid  into  sulphurous 
acid  and  free  sulphur,  which  is  precipitated.  The  only  one  of 
its  salts  which  possesses  any  interest  is  sodium  thiosulphate, 
Na2S2O8,  5  H2O,  the  commercial  name  for  which  is  "  hyposulphite  of 
soda."  This  salt,  is  largely  used  in  photography,  and  also  in 
bleacheries  as  an  "  antichlor  "  to  destroy  any  trace  of  "  bleaching 
chlorine  "  remaining  in  the  bleached  material.  Its  use  for  the 
latter  purpose  is,  however,  to  be  discountenanced  in  favor  of  the 
sulphites,  since  the  former  leaves  free  sulphur  in  the  fabric  by  its 
decomposition,  which  is  liable  to  work  injury,  while  the  sulphites 
are  merely  changed  to  comparatively  harmless  sulphates. 

Thiosulphate  of  sodium  is  easily  prepared  by  heating  a  solution  of 
sodium  sulphite  for  some  time  with  powdered  sulphur,  evaporating 
the  solution  and  crystallizing  out  the  salt.  It  forms  large,  color- 
less crystals  readily  soluble  in  water,  and  of  a  cooling  saline  and 
sulphurous  taste. 

The  cr}'stals  contain  five  molecules  (5  H2O)  of  water  of  crystal- 
lization. 

Sulphuric  Acid,  H2SO4;  commercial  name,  "Oil  of  Vitriol." 
—  This  acid  probably  holds  the  place  of  highest  importance  in  the 
arts  of  any  known  acids.  It  is  formed'  from  sulphurous  acid  by  the 
addition  of  an  atom  of  oxygen  to  the  molecule  of  the  latter, 


This  is  always  accomplished  slowly,  by  natural  means,  whenever 
sulphurous  acid  is  exposed  to  the  action  of  atmospheric  oxygen. 


46  GENERAL   CHEMISTRY. 

The  first  step  in  the  manufacture  of  sulphuric  acid  is  always  the 
burning  of  sulphur  (generally  in  pyrites)  into  sulphurous  anhy- 
dride, and  its  combination  with  moisture  into  sulphurous  acid. 
The  rapid  oxidation  of  the  latter  into  sulphuric  acid  is  accom- 
plished by  the  aid  of  nitrous  fumes,  produced  by  heating  mire ; 
oxygen  from  the  air,  and  steam.  Sulphurous  anhydride  from 
burning  sulphur,  nitrous  fumes,  steam,  and  air  are  introduced 
together  into  large  chambers  made  of  7  Ib.  sheet  lead. 

The  entire  course  of  the  reactions  which  take  place  in  the  cham- 
bers is  not  definitely  known.  A  very  small  amount  of  the  nitrous 
fumes  is,  however,  found  to  be  sufficient  to  cause  an  almost  un- 
limited amount  of  H2SOS  to  be  oxidized  tc  H2SO4,  the  nitrous 
f umesT  which  consist  of  a  mixture  of  several  oxides  of  nitrogen, 
apparently  acting  simply  as  carriers  of  oxygen,  alternately  giving 
up  a  portion  of  their  oxygen  to  the  sulphurous  acid,  and  renewing 
their  supply  from  the  air  present  in  the  chamber.  The  H2SO4,  as 
it  is  formed,  falls  as  a  fine  rain,,  and  collects  on  the  floor  of  the 
chamber,  diluted  with  the  condensed  water  from  the  excess  of 
steam  always  present  in  the  chamber.  This  dilute  acid  is  known 
as  "  chamber  acid,"  and  usually  contains  about  50  to  60  per  cent,  of 
real  H2SO4. 

This  chamber  acid  may  be  concentrated  to  a  gravity  of  about  1.78, 
and  containing  about  70  per  cent,  of  H^SO*,  by  evaporation  in  leaden 
pans,  when  it  is  technically  called  B.  O.  V.  (brown  oil  of  vitriol). 
Beyond  this  point  the  acid  begins  to  attack  the  lead,  and  must  then 
be  further  concentrated  in  vessels  of  glass  or  platinum.  The 
metal  is  most  used  on  account  of  the  liability  of  glass  to  breakage 
and  the  disastrous  effects  of  the  acid  when  this  occurs.  The  con- 
centration may  be  continued  until  oil  of  vitriol  is  obtained,  having 
a  gravity  of  1.84ra  boiling-point  of  338°  C.,  and  containing  100  per 
cent.  H2SO4. 

Sulphuric  acid,  H2SO4,  is  a  colorless  and  odorless,  heavy  liquid, 
of  an  oily  appearance.  It  freezes  at  —  26°  C.  It  chars  wood  and 
other  organic  bodies.  It  has  a  great  affinity  for  water,  absorbing 
more  than  its  own  volume  from  the  air  when  exposed  for  some 
time.  A  very  dilute  solution  of  H2SO4  has  the  property  of  chang- 
ing cellulose  and  starch  into  glucose  when  heated  with  them  for 
some  hours,  and  more  rapidly  under  high  pressures.  Sulphuric 
acid  of  1.60  specific  gravity  will,  at  a  temperature  of  £0°  C.,  dis- 
solve cellulose,  without  charring,  to  a  nearly  colorless  solution, 


SULPHURIC  ACID.  47 


which  may  be  diluted  with  Water  without  precipitation.  This 
property  of  the  acid  furnishes  an  easy  method  for  the  estimation 
of  total  cellulose  compounds  in  woody  materials,  since  the  non- 
cellulose  compounds  are  neither  charred  nor  dissolved  by  acid  of 
the  above  strength. 

Sulphuric  acid  unites  with  bases  to  form  sulphates,  all  of  which 
are  soluble  in  water  except  the  sulphates  of  barium,  strontium,  and 
lead.  Sulphate  of  lime  is  only  moderately  soluble,  one  part  of  the 
crystallized  salt,  CaSO4,2H2O,  requiring  400  parts  of  water  at 
15°  C.  for  solution. 

Quite  a  number  of  sulphates  are  of  natural  occurrence,  as  heavy 
spar  (barium  sulphate,  BaSO4),  gypsum  (calcium  sulphate, 
CaSO4,  2  H2O),celestine  (strontium  sulphate,  SrSO4),  and  Epsom 
salts  (magnesium  sulphate,  MgSO4,  7  H2O). 

"  Nordhausen,"  or  fuming,  sulphuric  acid,  which  is  H2SO4,  con- 
taining sulphurous  anhydride,  SO3,  is  obtained  by  distilling  dry 
ferrous  sulphate  (copperas),  FeSO4.  It  is  useful  as  a  solvent  for 
indigo  blue,  and.  is  mainly  consumed  in  the  manufacture  of  indigo 
extracts,  carmines,  etc. 

Sulphuric  anhydride,  SO8,  may  be  obtained  pure,  as  a  mass  of 
white,  silky  needles,  by  parsing  SO2  and  O  through  a  red-hot 
porcelain  tube  filled  with  spongy  platinum,  and  condensing  the 
vapors  in  an  air-tight  receiver,  surrounded  with  ice. 

Solid  SO3  has  a  specific  gravity  of  1.946.  It  melts  at  18.3°  C., 
and  boils  at  35°  C.  When  thrown  into  water  it  hisses  like  a  red- 
hot  iron,  and  dissolves,  forming  H2SO4.  SO3  is  soluble  in  all  pro- 
portions in  pure  H2SO4. 

The  remaining  aeids  of  sulphur  —  namely,  the  di-,  tri-,  tetra-,  and 
penfca-  thionic  acids  —  and  their  salts  ,are  of  no  commercial  value. 
They  are  all  unstable  acids,  which  are  known  only  in  combination. 
None  of  them  have  been  obtained  in  the  free  state.  They  are 
formed  to  some  extent,  in  the  sulphite  process,  through  the  action 
of  sulphurous  acid  upon  sulphur  vapor  when  overheating  of  the 
furnace  occurs.  The  dithionates  decompose  on  heating  into  SO2 
and  a  sulphate,  but  the  decomposition  of  the  higher  sulphur  acids 
is  attended,  with  separation  of  sulphur,  and  their  presence  in  sul- 
phite liquors  is,  on  this  account,  very  objectionable. 


48  GENERAL   CHEMISTRY. 

Sulphur  and  Nitrogen. 

Sulphur  forms  a  single  compound  with  nitrogen,  S2N2,  obtained 
by  passing  dry  ammonia  gas  through  a  solution  of  sulphur  di- 
chloride,  S2C12,  ui  carbon  disulphide.  It  forms  golden-yellow 
crystals,  insoluble  in  water.  It  explodes  when  heated  to  157°  C. 
Of  no  practical  interest. 

Sulphur  and  Carbon. 

When  vapor  of  sulphur  is  passed  over  red-hot  charcoal,  the  two 
combine  to  form  carbonic  sulphide,  or  carbon  bisulphide,  OS*. 
This  is  a  colorless,  very  inflammable  liquid,  of  specific  gravity  l.f>6, 
boiling  at  83°  C.  It  has  a  very  high  refracting  power.  When 
pure,  CS2  has  a  not  unpleasant  ethereal  odor :  but,  as  usually  met 
with,  it  possesses  a  very  repulsive  odor,  reminding  one  of  rotten 
cabbage. 

Bisulphide  of  carbon  is  of  considerable  importance  in  the  arts  as 
a  solvent  of  sulphur,  phosphorus,  iodine,  and  rubber  or  caout- 
chouc. It  is  also  a  free  solvent  of  fats  and  oils,  and  is  employed 
in  the  manufacture  of  certain  acid-proof  paints  from  asphalt,  and 
petroleum  residues. 

SELENIUM. 

Symbol,  Se.  — Atomic  weight,  79.5.  —  Molecule,  Se2 .  — Molecular  weight,  159. 

Selenium  is  a  reddish-brown  solid,  of  specific  gravity  4.3.  It 
melts  above  100°  C.,  and  boils  at  343°  C.  When  heated  in  the  air,  it 
has  an  extremely  disagreeable  odor  of  decayed  horseradish.  In  its 
properties  and  combinations  selenium  presents  a  very  close  analogy 
to  sulphur.  Selenium  has  never  been  found  native.  It  was  dis- 
covered by  Berzelius  in  1817.  It  is  of  no  importance  in  the  arts. 

TELLURIUM. 
Symbol,  Te.— Atomic  weight,  128.  —  Molecule,  Te2 .  — Molecular  weight,  256. 

This  substance  also  presents  a  close  analogy  to  sulphur,  but  in 
appearance  approaches  very  closely  to  the  metals,  being  lustrous 
like  silver.  The  specific  gravity  of  Te  is  6.26.  It  melts  below  a 
red  heat.  It  occurs  rarely  native  in  Hungary,  but  chiefly  in  com- 
bination with  other  metals  as  Tellurides.  Both  selenium  and 


CHLORINE. 


tellurium  often  occur  in  Japanese  sulphur.  Tellurium  was  first 
discovered  by  Miiller  in  1782.  Like  selenium  it  is  of  no  com- 
mercial importance. 

CHLORINE. 

Symbol,  Cl.  —  Atomic  weight,  35,5. —  Molecule,  C12  .•—  Molecular  weight,  71. 

Chlorine  is  a  yellowish-green  gas  of  specific  gravity  2.47  com- 
pared with  air.  It  is  uninflammable  and  irrespirable.  Water  at 
the  ordinary  temperature,  15°  C.,  dissolves  2.3  times  its  own  volume 
of  the  gas ;  it  also  combines  with  water  at  0°  C.  to  form  a  solid 
crystalline  hydrate  of  chlorine,  C12, 10H2O.  A  pressure  of  90  Ibs. 
at  a  temperature  of  0°  C.  condenses  the  gaseous  chlorine  into  a 
yellow  liquid  1.33  times  as  heavy  as  water. 

Chlorine  was  discovered  by  Scheele  in  1774.  It  never  occurs 
native,  but  always  in  combination  with  abase  as  a  metallic  chloride. 

Sea- water  contains  the  chlorides  of  potassium,  sodium,  calcium, 
and  magnesium,  each  in  considerable  amount.  Chlorine  has  a  very 
strong  affinity  for  the  metals  generally.  Many  of  them  when 
placed,  in  a  finely  divided  condition,  in  an  atmosphere  of  chlorine, 
combine  with  it  so  rapidly  as  to  be  raised  to  vivid  incandescence  by 
the  heat  of  the  chemical  action.  It  also  has  a  great  affinity  for 
hydrogen,  with  which  it  combines  to  form  hydrochloric  acid,  HC1. 
Many  hydrogen  compounds  are  at  once  decomposed  by  chlorine  in 
solution  with  the  formation  of  HC1  and  free  oxygen.  Chlorine  is 
a  powerful  disinfecting  and  bleaching  agent,  in  the  presence  of 
light  and  moisture.  Its  effect,  in  these  instances,  is  explained  by 
its  decomposition  of  water,  when  the  liberated  oxygen  destroys  the 
identity  of  the  disease  germs  in  the  one  case,  or  the  coloring- 
uiatter  in  the  other.  It  may  be  termed  a  powerful  secondary 
oxidizing  agent,  since,  though  not  itself  an  oxidizer,  it  produces  an 
oxidizing  action  through  the  agency  of  the  elements  of  water. 

Chlorine  and  Hydrogen. 

Hydrochloric  Acid.  —  Chlorine,  as  already  stated,  is  eager 
to  combine  with  hydrogen,  atom  for  atom,  both  being  univalent, 
forming  chloride  of  hydrogen,  or  hydrochloric,  commercially  called 
muriatic,  acid,  HCL 

This  is  a  colorless,  incombustible  gas,  of  specific  gravity,  com- 


50  GEXKRAL  CBEMI8TJBX. 

pared  with  air,  of  1»2?»  It  is  of  intensely  acid  taste,  and  pungent, 
irritating  odoiv  It  may  be  condensed  by  a  pressure  of  40  atmos- 
pheres, at  16*  (>.v  to  a,  colorless  liquid.  The  hydrochloric  or 
mviriivti&atiid  of  commerce  isy  however,  merely  a  solution  of  the  gas 
in  water,  wliieh  wilLdissolve,  at  0°  C.,  500  times  its  own  volume  of 
the  gas.  Ordinary  muriatic  acid  is  yellow  from  the  presence  of 
.chloride  of  iron,  and  it  frequently  also  contains  some  sulphuric 
aeid  Pure  hydrochloric  acid  is  colorless,  and  if  evaporated  on  a 
piece  of  glass  or  porcelain  leaves  no  residue-  Hydrochloric  acid  ia 
prepared  commercially  by  treating  chloride  of  sodium,  common 
salt,  with  sulphuric  acid,  the  torrents  of  hydrochloric  acid  which 
are  given  off  being  a  by-product  from  the  first  stage  of  the  Leblanc 
process  for  the  manufacture  of  soda.  The  gas  is  condensed  by 
passing  up  through  towers,  down  through  wliich  a  stream  of  water 
falls.  (See  Mintrfat>ttnns  of  Alkali.) 

Hydrochloric  aeid  is  a  monobasic  acid.  It  combines  with  the 
aietals-iu  genejal:  to  fonisr  metallic  chlorides,  with  the  liberation  of 
hydrogen.  With  the  metallic  oxides,  it  reacts  to  form  metallic 
chlorides  and  water.  A  single  molecule  of  HC1  requires  but  one 
atom  of  the  alkali  metals,,  which  have  a  valency  of  1  for  its 
saturation  ,  while  those  metals  whose  valency  is.  2,  as  the  alkaline 
earth  metals>  calcium  and  magnesium,  require  two  molecules  of*  the 
acid  for  each  atom  of  the  metal.  This  appears  in  the  following 
reactions  :  *•— 

4-aHei'.*  2  KaOl 

+  2LHCI  =  MgCl2 


Chlorine 

Chlorine  cannot  be  made  to  unite  with  oxygen  directly,  but  by 
indirect  means  throe  different  compound  of  these  two  elements 
may  be  formed  :  ~ 

Chlorine  dioxide  or  peroxide  ...    .     .    .     .     .     C1O2 

Hypochlorous  anhydride     .......    C12O 

Chl&rous  anhydride    .........     C18OS 

On  theoretical  grounds  there  is  some  reason  to  believe  that  the 
two  following  unknown,  compounds  might  exist:  — 

Chloric  anhydride  .. 
Perchloric  anhydride  .. 


JlYPOCHLOItOUS  ACID.  51 

Chlorine  dioxide  is  an  unstable,  dark-yellow  gas,  and  its  prepara- 
tion is  attended  with  danger,  on  account  of  the  tendency  of  the  gas 
to  decompose  spontaneously,  often  with  explosive  violence.  Its 
odor  suggests  those  of  chlorine  and  burned  sugar.  Kucldorine^ 
which  lias  powerful  bleaching  properties,  was  at  one  time  con- 
sidered a  distinct  oxide  of  chlorine,  but  is  now  known  to  be  a  mix- 
ture of  free  chlorine  and  chlorine  dioxide.  It  is  prepared  by 
treating  potassium  chlorate  with  hydrochloric  acid,  and  is  a  more 
active  decolorizer  and  disinfectant  than  chlorine  itself. 

The  anhydrides  of  chlorine,  as  such,  possess  little  practical 
interest;  but,  by  combination  with  the  elements  of  water,  the  cor- 
responding acids,  known  as  the  oxy-acids  of  chlorine*  are  formed, 
and  these  are,  in  some  easesv  of  the  highest  importance.  Thus  :—  - 


C12O  -fH2O  =  2HClO    .  .  Hypochlorous  a^id,  two  molecules. 

eiA4-H2O  =  2HClO8  .  .  Chlorous  acid,  "  " 

01  A  4-  H2O  =  2  HC103  .  .  Chloric  acid,  "  " 

CIA  +  H2O  =  2  HC1O4  .  .  Perchloric  acid,          "  « 

Hypochlorous  Acid,  HC1O.  —  The  first  of  the  oxy-aoids  of 
chlorine,  or  that  containing  the  least  oxygen,  is  hypochlorous  acid. 
Free  HC1O  is  formed  when  hypochlorous  anhydride,  C12O  (formed 
as  a  yellow-colored  gas  by  treating  mercuric  oxide,  HgO,  with 
chlorine),  is  passed  into  water.  One  volume  of  water  will  dissolve 
200  volumes  of  the  gas.  Free  HC1O  is  also  formed  when  a  dilute 
solution  of  hydrochloric  acid  is  submitted  to  electrolysis  with 
platinum  electrodes*  In  this  case  the  water  and  HC1  are  simul- 
taneously decomposed  by  the  electricity,  the  chlorine  and  oxygen 
appearing  at  the  positive  electrode,  where  they  unite  with  each 
other  and  combine  with  water  to  form  TIC1O,  while  hydrogen 
escapes  as  gas  at  the  negative  electrode.  Thus  :  — 

2HC1  -f  2  HA  electrolyzed,  become  2HC1O  -f  2H2. 

Hypochlorous  acid  is  a  very  unstable  compound,  the  oxygen 
atom  being  apparently  very  loosely  held  in  the  molecule.  The 
presence,  in  a  solution  of  this  acid,  of  almost  any  oxidizable  sub- 
stance is  sufficient  to  determine  the  reduction  of  the  HC1O  mole* 
cule  to  a  molecule  of  HC1,  while  the  other  substance  present  passes 
to  a  higher  state  of  oxidation.  On  this  account  hypochlorous  acid 
is  a  very  powerful  bleaching  agent,  giving  up  its  oxygen  with  great 


GEN  SEAL   CHEMISTRY. 


readiness  to  the  coloring-matter  of  the  material  to  be  bleached, 
either  forming  with  it  colorless,  soluble  compounds,  or  ultimately 
burning  it  to  carbonic  acid  gas  and  water.  Free  hypochlorous  acid 
being,  however,  so  difficult  of  preparation,  and  of  so  little  stability, 
that  it  cannot  be  preserved  for  any  length  of  time  in  solution,  plays 
no  important  part  in  the  arts.  It  unites  with  the  alkali  and 
alkaline  earth  metals  to  form  hypochlorites,  which  are  much  more 
stable  compounds  than  the  free  acid.  Common  bleaching-powder, 
for  example,  which  consists  (at  least  when  dissolved)  of  calcium 
hypochlorite,  CaCl2O2,  mixed  with  varying  proportions  of  calcium 
chloride,  CaCl2,  and  calcium  hydrate,  CaH2O2,  may  be  preserved 
for  a  considerable  time,  with  only  slow  deterioration.  (See  Bleach- 
ing.) Even  in  solution,  the  oxidizing  or  bleaching  action  of  the 
hypochlorites  is  much  less  rapid  than  that  of  the  free  acid,  as  may 
be  shown  by  the  addition  of  acetic  acid,  for  example,  to  a  solution 
of  calcium  hypochlorite,  and  observing  the  action  of  portions  of  the 
solution,  before  and  after  the  addition  of  acid,  upon  two  portions 
of  unbleached  pulp.  The  acetic  acid  in  this  case  combines  with 
the  lime,  leaving  the  hypochlorous  acid  free.  Nor  do  all  the  hypo- 
chlorites act  as  oxidizing  or  bleaching  agents  with  the  same  energy 
and  rapidity,  aluminum  hypochlorite  being  probably  the  most 
rapid  in  its  action,  while  sodium  hypochlorite  is  probably  the  slow- 
est. The  magnesium  salt  acts  more  rapidly  than  the  calcium  salt. 
(Compare  Electric  Bleaching,  Chap.  X.)  The  mode  of  action  of 
the  hypochlorites  in  the  process  of  bleaching  is  the  same  as  in  the 
case  of  the  free  acid  ;  namely,  the  transference  of  the  oxygen  of  the 
acid  to  the  organic  coloring-material,  the  hypochlorous  acid,  in 
both  cases,  being  the  bleaching  agent,  or,  better,  furnishing  the 
bleaching  oxygen. 

Manufacture  of  Bleaching-Powder.  —  Chlorine  is  usually 
prepared  for  use  in  the  arts  by  the  action  of  hydrogen  chloride, 
HC1  (hydrochloric  or  muriatic  acid),  on  dioxide  of  manganese,  the 
equation  for  the  reaction  being  — 

MnO2  +  4  HC1  ==  MnCl2  (Manganous  chloride)  +  2  H20  +  C12. 

By  "  Weldon's  Process,"  which  consists  in  treating  the  solution  of 
manganous  chloride  with  hot  milk  of  lime  or  magnesia,  and  blow- 
ing hot  air  through  the  mixture,  the  manganese  may  be  recon- 
verted into  manganese  dioxide  to  be  used  afresh  in  the  manufac- 
ture of  chlorine.  "  Deacon's  Process  "  for  the  manufacture  of 


BLEA  CHING-PO  WDEB .  58 

chlorine  consists  in  passing  a  mixture  of  gaseous  hydrochloric  acid 
and  air  over  copper  sulphate,  heated  to  about  370°  C.  By  the 
electrolysis  of  many  of  /the  metallic  chlorides  in  a  fused  state,  or 
strong  solution,  chlorine  is  obtained  at  the  positive  electrode,  and 
the  metal  at  the  negative  (Part  II.,  Chap.  x.). 

Bleaching-powder,  "  chloride  of  lime,"  or  properly,  calcinm  hypo- 
chlorite,  is  prepared  by  passing  chlorine  over  slaked  lime,  exposed 
in  shallow  layers  to  the  action  of  the  gas.  The  absorption 
chambers  are  usually  60  feet  long,  18  feet  wide,  and  7  feet  high. 
They  are  built  sometimes  of  large  flag-stones,  but  more  generally 
of  8-lb.  lead,  supported  by  a  framework  of  scantling.  The  floor  is 
made  of  brick,  laid  in  tar  cement  over  a  sheet  of  lead.  Where  the 
Deacon  process  is  worked  the  chambers  are  divided  into  sections 
fitted  with  shelves,  upon  which  the  lime  is  placed ;  but  in  other 
cases  the  lime  is  spread  upon  the  floor  in  a  layer  from  four  to  five 
inches  deep,  and  is  then  raked  into  furrows. 

The  chlorine  is  admitted  to  the  chambers,  and  is  at  first  rapidly 
absorbed  by  the  lime  with  evolution  of  heat.  After  the  lime  is 
nearly  charged  the  supply  of  gas  is  shut  off,  so  that  the  chlorine 
remaining  in  the  chambers  may  be  gradually  taken  up.  This 
requires  four  or  five  days,  and  the  entire  treatment  about  a  week. 

The  quality  of  bleaching-powder  depends  very  much  upon  that 
of  the  lime  from  which  it  is  made,  and  in  order  to  secure  the  best 
bleach  the  lime  must  be  especially  pure.  A  "  fat  lime,"  or  one 
which  slakes  easily,  is  best  for  the  purpose,  as  it  absorbs  chlorine 
more  quickly  and  keeps  best.  Iron  and  manganese  are,  of  course, 
objectionable  in  the  lime,  on  account  of  the  color  which  they  im- 
part to  the  bleaching-powder,  and  they  are  also  said  to  impair  the 
keeping  qualities  of  bleach  in  which  they  occur. 

Clay  and  silica  injure  the  quality  of  bleach,  since  they  cause  it 
to  settle  slowly  and  imperfectly ;  while  bleach  containing  magnesia 
has  an  increased  tendency  to  take  up  water  and  become  pasty 
through  the  formation,  according  to  Lunge,  of  magnesium  chloride. 

In  order  to  prepare  bleaching-powder  it  is  necessary  that  the 
lime  contain  some  water.  Partially  slaked  lime  maybe  imperfectly 
chlorinated,  but  the  best  results  are  obtained  when  dry  chlorine  is 
used  and  the  slaked  lime  contains  2  to  4  per  cent,  excess  of  water. 
The  temperature  at  which  absorption  takes  place  has  a  decided 
influence  upon  the  strength  and  quality  of  the  product,  through 
the  formation  of  chlorate  at  the  higher  temperatures.  The  best 


54  GENERAL   CHEMISTRY* 

authorities  prefer  a  temperature  not  above  40°  to  66°  0.  Hurter 
gives  as  the  maximum  40° ;  Bobierre,  50° ;  Sheurer-Kestner,  55°. 
The  experiments  of  Schappi,  who  used  moist  chlorine,  gave  at — -. 

Temperature  Available  chlorine       Temperature  Availabte  chloride 

c-C.  percent.  «C.  j*r  certt. 

—  17 2.30  40 41.18 

0 19.88  45 40.50 

7  .  V"*.  .     .  33.24  50 41.52 

21 35,50  60 39.40 

21  (25?)      .     .  39.50  90 4.26 

30 40.10 

Good  bleach  should  be  a  pure  white  powder,  containing  some 
lumps  if  the  test  is  high,  and  having  a  faint  odor  of  hypochlorous 
acid.  It  should  become  tough  when  kneaded  with  the  fingers. 
The  lumps  should  not  contain  a  core  of  lime,  but  should  be  con- 
verted to  bleach  throughout,  and  should  break  down  easily  between 
the  fingers.  The  formula  usually  given  for  bleaching-powder  is 
CaCl2O2,  but  the  latest  experiments  of  Lnnge  point  to  the  formula 
CaOCl2.  There  is  usually  present  also  a  little  calcium  chlorate, 
chloride,  and  free  lime. 

Chlorous  Acid,  HC1O2.  — This  acid,  containing  one  more  atom 
of  oxygen  in  its  molecule,  is  formed  by  the  action  of  nitric  acid 
on  potassium  chlorate.  It  is  never  met  with  ordinarily  in  the 
free  state,  as  it  is  a  dangerous  compound.  In  combination  with 
bases,  however,  as  chlorites,  it  is  of  not  infrequent  occurrence. 
Chlorites  are  formed  by  the  electrolysis  of  solutions  of  the  alkali 
and  alkaline  earth  chlorides,  under  regulated  conditions.  They 
are  bleaching  agents  of  less  enei  »y  than  the  hypochlorites,  and  are 
of  little  importance. 

Chloric  Acid,  HC1O3.  —  This  acid  is  of  no  importance  in  the  free 
state.  Its  chief  salt  of  commerce  is  potassium  chlorate,  KC1O8.  A 
solution  of  this  salt  does  not  bleach  in  the  cold,  but  on  heating, 
with  the  addition  of  a  mineral  acid,  it  oxidizes  organic  matter  with 
great  energy.  The  dry  salt  forms  powerful  explosive  mixtures 
with  sulphur,  phosphorus,  irmny  of  the  minerals,  and  organic 
matter  generally.  A  mixture  of  sugar  and  chlorate  of  potassium, 
powdered  separately,  and  cautiously  mixed  to  avoid  friction,  will 
be  set  on  fire  by  a  drop  of  strong  sulphuric  acid.  Potassium 
chlorate  is  formed  by  passing -* a  stream  of  chlorine  gas  through  a 
warm  solution  of  caustic  potash.  Chlorates  are  also  formed  by  the 


BRGMltfE.  55 


electrolysis  of  solutions  of  the  chlorides,  under  ,  certain  coniliiiVms 
of  strength  of  solution  and  current,  and  especially  of  tempera- 
ture of  solution,  elevation  of  temperafciure  -.fevering  their  forma- 
tion at  the  expense  of  that  of  the  hypochlorrtes.  Chlorate  df  lime 
occurs  in  small  and  vary  ing  -percentage  in  bleaeliing-powder. 

Perchloric  Acid,  HCiO4  .  —  This  is  a  colorless,  volatile  liquid, 
and  is  a  very  powerful  oxidizing  agent.  It  fornii  perch  lorates. 
Neither  the  acid  nor  its  salts  are  of  any  importance  except  as 
chemical  reagents. 

Chlorine  and  Nitrogen. 

Chlorine  combines  with  nitrogen  to  form  a  single  compound, 
which  we  mention  here  simply  'on  account  of  its  -^extremely  danger- 
ous character.  It  is  an  oily  liquid,  heavier  than  water.  It  explodes 
spontaneously,  and  with  extreme  violence,  below  109°  C.  Its 
iormula  is  probably  NC18.  It  is  formed  by  the  action  of  chlorine 
gas  on  a  strong  solution  of  chloride  of  ammonia,.  sal  ammoniac,  and 
also  when  such  a  solution  of  sal  ammoniac  is  electrdly  zed. 


Chlorine  and 
Chlorine  combines  directly  with  sulphur,  formrng  — 


Sulphur  chloride  .. 
•Sulphur  dichloride  .  . 
Sulphur  tetra-chloride 


These  compounds  are  all  liquids  of  some  vriiue  to  the  chemiit,  but 
having  few  practical  applications. 


BttOMIME 

Symbol,  Br.  —Atomic  weight,  80^—  Mo&eul^iBrj.,  —  MoteeiiUr  -\veigh  t,  160. 
Bromine  is  a  deep-red  liquid  of  i^p»oiric  gravity  '£.9-76.  It  freezes 


at  —  24  £-°C.,  and  boils  at  63°  G.  It  volatilizes  rapidly  at  ordinary 
temperatures  in  xed  fumes  ef  »  iserjr  disagreeable  odor,  am!  ex- 
tremely irritating  to  the  tnuoouB  menibraue  of  ike  throat  and  eyes. 
Bromine  is  little  ftwluble  in  water,  more  readily  in  alcohol' 
ether.  Bromine  was  discovered  by  Balard  in  1826.  It 
in  combination  with  alkaline  bases,  in  sea-water,  and  in  the  water 
of  many  mineral  springs.  It  never  occurs  native. 


56  GENERAL   CHEMISTRY. 

Bromine  resembles  chlorine  very  markedly  in  all  its  properties, 
forming  throughout  analogous  compounds.  In  chemical  activity, 
however,  it  is  somewhat  less  energetic.  It  finds  many  uses  in  tne 
arts  and  in  medicine ;  but,  aside  from  its  close  relation  to  chlorine, 
is  of  little  interest  to  the  paper-maker. 


IODINE. 

Symbol,  I.— -Atomic  weight,  127.  —  Molecule,  I2 .  —  Molecular  weight,  254. 

Iodine  bears  great  resemblance  in  its  chemical  properties  to 
chlorine  and  bromine,  but  differs  from  both  in  being,  at  ordinary 
temperatures,  a  solid  crystalline  substance,  of  a  steel-blue  color 
and  metallic  lustre.  It  has  a  specific-  gravity  of  4.95.  Iodine 
melts  at  107°  C.,  and  boils  at  175°  C.,  the  vapor  having  a  deep 
violet  color.  It  volatilizes  quite  rapidly  at  ordinary  temperatures. 
Iodine  is  very  slightly  soluble  in  water,  but  easily  in  alcohol  and 
in  a  solution  of  potassium  iodide. 

It  was  discovered  by  Courtois  in  1811,  in  the  ash  of  sea- weeds. 
It  occurs  usually  as  sodium  iodide  in  sea-water  and  in  many 
mineral  springs.  Iodine  never  occurs  native.  It  is  of  great  value 
both  free  and  in.  combination  in  medicine,  and  finds  many  uses  in 
the  arts. 

Its  compounds  are  all  analogous  to  those  of  chlorine  and  bromine. 
A  solution  of  iodine  in  potassium  iodide  is  of  great  value  in  the 
sulphite  pulp  process,  since  it  furnishes  a  ready  means  of  deter- 
mining the  total  amount  of  sulphurous  acid  in  the  bisulphite  solu- 
tion used.  (Compare  Analysis  of  Bisulphite  Liquors.) 


FLUORINE. 

Symbol,  F.— Atomic  weight,  19. —  Molecule,  F8 .  — Molecular  weight,  38. 

Fluorine  is  an  extremely  energetic  and  corrosive  gaseous  ele- 
ment, never  found  native.  It  forms,  with  hydrogen,  hydrofluoric 
acid,  HF,  corresponding  to  hydrochloric  acid,  and  is  interesting 
from  its  property  of  dissolving  or  etching  glass  ;  hence  it  must  be 
preserved  in  leaden  or  gutta-percha  bottles.  Hydrofluoric  acid 
is  a  dangerous  substance  to  handle,  owing  to  its  injurious  action 
on  the  throat  and  lungs.  The  chief  natural  compounds  of  fluorine 
are  calcium  fluoride,  or  fluorspar,  CaF2,  and  sodium-aluminum 


BORON.  57 


fluoride,  or  cryolite,  3  NaF,  A1F3.  The  latter  is  the  raw  material 
from  which  "  Natrona  "  alum  and  "  Natrona  "  bicarbonate  of  soda 
are  made.  It  is  obtained  from  Greenland. 

These  four  elements  —  chlorine,  bromine,  iodine,  and  fluorine  — 
are  often  classed  together  as  the  chlorine  group,  from  their  similar- 
ity in  their  chemical  characters,  and  in  the  formation  and  nature 
of  their  compounds. 

They  are  also  sometimes  denominated  the  halogens,  and  their 
compounds  the  halogen  compounds.  It  is  interesting  to  note  in 
this  connection  how  the  chemical  activity  of  the  members  of  the 
group  falls  as  the  atomic  weight  rises. 

BORON. 

Symbol,  B.  —Atomic  weight,  11.  —  Molecule,  B2 .  —  Molecular  weight,  22. 

Boron  is  a  solid  element,  never  native,  and  of  no  interest  except 
in  combination.  It  has  a  valency  of  three,  one  atom  being  the 
equivalent  of  three  atoms  of  hydrogen  in  combining  power.  Thus 
it  forms  with  chlorine,  BC13,  boron  chloride,  and  with  fluorine, 
BF3,  boron  fluoride.  The  latter  is  interesting  as  being  one  of  the 
few  reagents  which  give  a  direct  qualitative  reaction  with  cellulose, 
which  is  blackened  by  boron  fluoride. 

Boron  always  occurs  in  nature  combined  with  oxygen  as  boracic 
acid  (or  boric  acid),  H3BO3,  either  free  or  in  combination.  Boracic 
acid  is  soluble  in  three  parts  of  boiling  water,  from  which  it  crys- 
tallizes on  cooling  in  pearly,  mica-like  scales,  requiring  25  parts 
of  water  at  18°  C.  for  solution.  Boracic  acid  is  soluble  in  alcohol, 
and  when  alcohol  containing  it  in  solution  is  burned  the  acid  im- 
parts a  green  color  to  the  flame. 

The  chief  salt  of  boracic  acid  is  borax,  sodium  biborate, 
Na2B4O7 ,  10  H2O,  which  is  found  native  in  large  quantities  in  Cali- 
fornia and  certain  other  places.  Borax  is  of  considerable  use  in 
the  working  of  iron  and  many  other  metals,  from  its  property  of 
dissolving  or  forming  a  flux  with  many  metallic  oxides  when  fused 
with  them.  Borax  possesses  marked  detergent  qualities,  owing 
largely  to  the  power  of  its  solutions  of  dissolving  and  partly 
saponifying  fatty  matters.  It  also,  when  in  solution,  forms  a  ready 
solvent  for  shellac,  one  part  of  borax  being  sufficient  to  render 
soluble  about  five  parts  of  shellac.  Alum  and  lime  salts  reprecip- 
itate  the  gum. 


58  MBXRAL  CHEMISTRY. 

Solutions  of  boraeic  acid  and  its  -salts  possess  quite  marked 
antiseptic  properties,  and  011  that  account  are  t>f  considerable  im- 
portance. They  also  possess  medicinal  properties. 


SILICON. 

Symbol,  Si. —  Atomic  weight,  28. 

Silicon  never  occurs  native,  but  combined  with  oxygen  as  silicic 
anhydride,  SiO2,  or  -silica,  it  is  one  of  the  most  abundant  of 
minerals.  The  elementary  substance  was  first  isolated  by  Berzelius 
in  1823.  It  may  be  prepared  with  some  difficulty  in  two  forms, — 
amorphous  silicon,  a  brown  powder  heavier  than  water,  and  a,  non- 
conductor of  electricity;  and  crystalline  silicon,  a  steel-gray  sub- 
metallic  crystalline  .substance  of  specific  gravity  2.49,  and  which  is 
a  conductor  of  electricity.  By  electrolysis  of  certain -compounds  of 
silica,  in  a  state  of  Busion  with  metallic  compounds,  alloys  of  silicon 
may  be  obtained.  They,  howieyer,  present  more  of  the  characters 
of  a  solution,  if  we  may  so  term  it,  of  the  silicon,  in  the  metal  than 
of  true  homogeneous  alloys.  Hock  crystal,  or  quartz,  is  pure  silica, 
SiO2»  Amethyst,  agate,  flint,  carnelian,  onyx,  etc.,  are  nearly  pure 
fiiltea,  colored  by  small  quantities  of  metallic  oxides.  By  fusion 
with  carbonate  of  soda,  silicate  of  soda  is  formed,  which  is  a  sub- 
stance having  the  <appearance  of  glass,  but  soluble  in  water,  hence 
called  soluble  glass.  Ordinary  glass  is  a  more  or  less  pure  silicate 
of  lime,  containing  some  soda  and  some  metallic  oxides,  as  man- 
ganese, lead,  and  iron  oxides. 

Ordinary  cl&y  is  a  -mixed  silicate  of  alumina,  lime,  magnesia,  etc., 
usually  contairuDg  other  metallic  silicates,  which  give  it  color. 
Kaolin,  or  china  clay,  is  very  nearly  pure  silicate  of  aluminum, 
the  impurities  being  varying  amounts  of  silicates  of  lime  and  mag- 
nesia. It  contains  no  iron  or  other  colored  metallic  oxides. 

The  value  of  a  clay  for  a  paper-maker's  use  is  largely  dependent 
on  the  proportion  of  silicate  of  alumina  it  contains,  and  its  freedom 
from  iwm  oxide,  sand,  and  grit. 

Silicon  forms  compounds  with  chlorine,  bromine,  iodine,  and 
fluorine,  SiCl4,  SiBr4,  SiI4,  and  SiF4.  They  are  solely  of  interest 
and  use  to  the  chemist. 


PHOSPHORUS.  59 


PHOSPHORUS. 

Symbol,  P.  —  Atomic  weight,  31.  —  Molecule,  P< .  —  Molecular  weight,  124. 

Phosphorus  is  a  translucent,  slightly  yellow  substance  of  specific 
gravity,  1.83,  and  resembling  wax  in  appearance.  It  possesses  a 
peculiar  odor  suggestive  of  garlic.  It  melts  at  44°  C.,  and  boils 
at  290°  C.  It  is  insoluble  in  water ;  somewhat  soluble  in  ether, 
turpentine,  and  oils.  It  is  freely  soluble  in  carbon  disulphide. 

Phosphorus  was  discovered  by  Brandt  in  1669.  It  takes  its 
name  from  two  Greek  words  meaning  "  light-bearer,"  and  was  so 
called  on  account  of  its  property  of  emitting  light  when  exposed  16 
the  air. 

It  is  never  found  native,  but  in  combination  with  lime  is  widely 
distributed  in  nature.  It  forms  an  essential  element  in  the  com- 
position of  the  bones,  blood,  brain,  and  other  portions  of  the 
animal  economy,  and  is  always  necessary  to  the  development  of 
seed  in  plants. 

Although  in  combination  with  oxygen  it  is  so  essential  to  animal 
life,  yet  in  the  free  state  it  forms  a  virulent  poison,  excepting  in 
a  single  one  of  its  amorphous  forms.  This  latter  modification^ 
known  from  its  color  as  red  phosphorus,  is  prepared  by  Iieating 
ordinary  phosphorus  in  an  atmosphere  of  carbonic  anhydride  for 
thirty  or  forty  hours,  at  a  temperature  of  230°  to  240°  C.  It  then 
forms  a  red  powder,  insoluble  in  all  media.  It  is  non-poisonous, 
and  does  not,  like  ordinary  phosphorus,  need  to  be  preserved  under 
water,  as  the  red  variety  does  not  inflame  below  260°  C.  Phos- 
phorus is  prepared  from  calcium  phosphate,  by  distillation  with 
charcoal,  the  vapors  of  phosphorus  produced  being  condensed  and 
the  resulting  phosphorus  preserved  under  water.  On  account  of 
its  inflammability  phosphorus  is  a  very  dangerous  substance,  and 
must  be  kept  under  water  and  handled  with  extreme  care. 

Phosphorus  forms  a  great  variety  of  compounds  of  extended  use 
in  medicine  and  in  the  arts,  but  none  have  any  immediate  bearing 
on  the  art  of  paper-making,  and  on  that  account  may  be  omitted 
here. 

Phosphorus  combines  directly  with  metals,  when  heated  with 
them,  to  form  phosphides  of  the  metals,  and  in  many  cases  the 
phosphides  may  be  alloyed  directly  with  other  metals.  When 
present  in  very  small  quantities  the  phosphides  serve  to  impart  to 
anetals  characters  quite  distinct  froin<  those  of  the  pure  metals. 


60  GENERAL   CHEMISTRY. 

In  most  cases  the  presence  of  phosphorus  in  a  metal  is  objec- 
tionable, while  in  a  few  instances,  as,  for  example, in  "phosphor 
bronze,"  it  imparts  very  useful  properties  to  the  metal  or  alloy. 
Phosphor  bronze  is  an  alloy  of  copper  and  tin,  and  contains  a 
small  amount  of  phosphide  of  tin,  which  gives  the  alloy  marked 
acid-resisting  quality,  besides  increasing  its  strength  and  tough- 
ness. 

ARSENIC. 

Symbol,  As.  — Atomic  weight,  75.  —  Molecule,  A^.  —  Molecular  weight,  300. 

Arsenic  is  sometimes  found  native,  but  -more  commonly  occurs 
in  combination  with  metals  and  sulphur  as  sulpho-arsenides.  Ar- 
senic um,  as  it  is  frequently  written,  occupies  the  border  line  be- 
tween the  non-metallic  substances  and  the  metals.  In  its  phys- 
ical characters,  and  in  its  combinations  with  sulphur,  it  approaches 
more  nearly  the  metals;  while  in  the  formation  of  anhydrides, 
As2O3  and  As2O5,  and  .their  corresponding  acids,  H3AsO8  and 
HaAsO4,  as  well  as  in  most  of  its  other  chemical  characters,  it 
plays  the  part  of  a  non-metal.  Pure  arsenic  is  a  steel-gray  sub- 
stance, having  a  bright,  metallic  lustre.  It  tarnishes  rapidly  in  the 
air.  Its  specific  gravity  -is  about  5.8.  Heated  in  the  air,  it  burns 
with  a  bluish  flame.  Nearly  all  the  compounds  of  arsenic  are 
extremely  poisonous.  The  common  arsenic  of  the  shops,  or  white 
arsenic,  is  arsenious  anhydride,  As2O8.  Paris  green  is  aceto- 
arsenite  of  copper. 

The  common  rat-poisons  and  potato-bug  poisons  are  nearly  all 
preparations  of  arsenic.  Some  of  the  compounds  of  arsenic  are  of 
great  use  in  the  arts.  In  the  manufacture  of  aniline  colors  many  of 
the  most  brilliant  and  beautiful  shades  are  best  obtained  by  the  use 
of  compounds  of  arsenic.  In  these  colors  it  is  the  aim  of  the  manu- 
facturer to  remove  the  arsenic  in  a  subsequent  process  of  the 
manufacture.  Unfortunately  the  removal  is  often  incomplete,  and 
numerous  cases  of  arsenical  poisoning,  more  or  less  acute,  have 
occurred  from  the  presence  of  arsenic  in  the  colors  of  wall-paper  or 
in  the  dye  of  carpets  or  clothing.  The  presence  in  wall-paper  of 
the  equivalent  of  a  quarter  of  a  grain  of  white  arsenic  per  square 
yard  is  considered  dangerous. 

Arsenious  acid  in  solution,  either  in  hydrochloric  acid  or  dis- 
solved in  water  as  arsenite  of  soda,  is  readily  oxidized  by  chlorine, 


ARSENIC.  61 


or  a  hypoehlorite,  into  arsenic  acid,  and  so  furnishes  the  analyst 
with  a  ready  means  of  determining  the  "available  chlorine"  in  a 
solution  of  bleaching-powder.  (Compare  Analysis  of  Bleaching- 
powder.) 

The  preceding  fifteen  elements  comprise  all  the  non-metallic 
elements  at  present  known.  The  oxides  of  all  these  elements  are 
called  anhydrides,  and  unite  with  water  to  form  acids,  either  mono- 
basic, di-,  tri-,  or  tetra-  basic,  according  as  they  contain  respectively 
one,  two,  three,  or  four  atoms  of  hydrogen,  which  may  be  replaced 
by  a  metal. 


62  GENERAL  GHEM1STSY. 


THE   METALLIC  ELEMENTS. 

THBK»  are  at  least  forty-nine  known  metals.  Many  of  them 
tire,  however,  of  small  importance,  and  indeed  have  been  but  little 
investigated. 

All  the  metals  combine  with  oxygen  to  form  oxides,  which  iu 
turn  may  unite  directly  \\ ith  anhydrides  (oxides  of  the  non-metals) 
to  form  salts.  The  oxides  of  the  non-metals  (anhydrides)  unite 
with,  water  to  form  acids,  while  the  metallic  oxides  unite  with 
water  to  form  hydroxides,  sometimes  called  hydrates  or  bases. 
Acids  a.nd  hydroxides  unite  to  form  metallic  salts,  with  theelimina 
tion  of  water;  thus,  hydrochloric  acid,  IIC1,  and  sodium  hydroxide, 
NaHO,  unite  to  form  sodium  chloride,  NaCL  and  water,  H/)  — 

HC1  -f  KallO  =  NaCl  -f  H2O. 

A  few  of  the  metals  form  both  acid  and  basic  oxides,  standing 
as  it  were  on  the  dividing-  line  between  the  non-metals  and  the 
metals. 

A  very  large  proportion  of  the  oxides  are  insoluble  in  water,  and 
also  most  of  the  metallic  salts,  with  the  exception  of  the  chlorides, 
nitrates  and  sulphates,  which  are  nearly  all  soluble  in  water. 

The  metals  are  all  good,  though  not  equally  good,  conductors  of 
heat  and  electricity.  They  are  all  opaque  substances,  capable  in 
the  mass  of  receiving  a  more  or  less  polished  surface,  and  they 
exhibit  a  peculiar  lustre,  termed  metallic.  They  show  various 
degrees  of  hardness,  from  the  consistency  of  putty  to  the  hardness 
of  steel.  The  brittleness  of  metals  is  much  increased  by  lowering 
of  temperature.  All  exhibit  a  considerable  degree  of  tenacity,  or 
resistance  to  a  breaking  strain.  Many  of  the  metals  are  malleable ; 
that  is,  may  be  extended  under  rollers  or  beaten  into  sheets.  In 
the  latter  regard  gold  takes  the  first  rank.  Gold  leaf  may  be  made 
on)y  -ffdtto  °^  an  *ncn  i*1  thickness. 

The  specific  gravity  of  the  metals  varies  greatly,  lithium  being 
the  lightest,  specific. gravity  0.59,  and  osmium  the  heaviest,  specific 
gravity  22.48. 


POTASSIUAf.  63 


Many  of  the  metals  occur  in  nature  in  the-  form  of  crystals'.  The 
metals  combine  together  under  the  influence  of  heat  to  form  alloys, 
the  melting-point  of  the  alloy  often  being  below  that  of  any  of  the 
constituent  metals.  The  alloys  appear,  in  some  respects,  to  be  true 
chemical  compounds,  but  are  not  in  general  so  regarded.  Alloys 
of  mercury  are  called  Amalgam*. 

THE  ALKALI  META&S. 

The  alkali  metals  are  six  in  number :  — 


Potaaaium  :: 

Symbol, 

K.  —  Atomic    weight,  39.  1 

Sodium  : 

Symbol, 

^  a.  ~      **- 

«       23. 

lathiuiu:: 

Symbol, 

Li.  —       *** 

'        7. 

Caesium: 

Symbol, 

Cs.  —      « 

*     133. 

Rubidium; 

P  A  mrngmiimi 

Symbol, 
1  :  Svmbol. 

Rb.  —      «• 
NHL  —  Combiuins 

'      85.4 
•       18. 

The  alkali  metals  all  have  a  valency  of  1;  that  is,  are  capable  of 
replacing  the  hydrogen  of  an  acid  atom  for  atom.  Their  hydrox- 
ides are  very  soluble  in  water,  and  their-  solutions  are  strongly 
alkaline  to  test  paper,  and  caustic  and  destructive  in  their  action 
upon  animal  substances.  Their  carbonates  are  soluble  in  w-ater, 
and  these  solutions  are  also  alkaline. 

POTASSIUM. 
Symbol,  K.  —  Atomic  weight,  39.1.  —  Specific  gravity,  0.865; 

Potassium  is  a  brilliant,  bluish-white  metal,  which  melts  at 
62^  C.,  and  volatilizes  at  a  red  heat  in  green  vapors.  It  is  never 
found  native,  but  its  compounds  are  widely  distributed,  being 
found  in  mica,  feldspar,  all  fertile  soils,  sea-water,  and  in  large 
quantities  in  the  salt  deposits  at  Stassfurt,  Germany.  The  metal 
oxidizes  so  rapidly  that  it  has  to  be  preserved  under  naphtha  or 
some  other  liquid  which  contains  no  oxygen.  When  thrown  upon 
water  it  decomposes  the  latter,  uniting  with  the  oxygen,  and;  dis- 
solving as  hydroxide,  KHO,  and  setting  free  the  other  atom  of 
hydrogen.  So  much  heat  is  developed  i»  the  reaction  that  the 
hydrogen  takes  fire,  its  flame .  being  colored  violet  by  the  vapor  of 
potassium.  This  violet-colored  flame  furnishes  a  ready  test  for  the 
metal. 

Potassium  oxide+  K2O,  is  the  potash  of  chemists.  It  is  formed 
by  the  dry  oxidation  of  potassium.  It  unites  with  water  molecule 


64  GENERAL   CHEMISTRY. 

for  molecule  (K2O  4-  H2O  =  2  KHO)  to  form  potassium  hydroxide, 
or  hydrate,  KHO,  commercially  called  caustic  potash.  This  is  a 
hard,  grayish-white  solid,  which  dissolves  very  readily  in  water, 
with  development  of  much  heat.  It  attracts  moisture  from  the 
air  so  rapidly  as  to  become  liquid  in  a  short  time.  This  action  is 
called  deliquescence.  Potassium  hydrate  is  a  very  caustic  and 
powerful  base.  It  precipitates  the  metals  as  hydrates  from  nearly 
all  solutions  of  metallic  salts.  It  forms  compounds  with  all  the 
acids,  many  of  these  compounds  being  of  great  importance.  With 
fats  and  oils  it  forms  hard  soaps,  while  soda  forms  soft  soaps. 

Potassium  carbonate,  K2CO3,  is  veiy  similar  to  soda-ash,  which 
is  sodium  carbonate.  The  crude  potassium  salt  is  obtained  from 
wood  ashes  by  leaching  them  and  evaporating  the  solution,  and 
is  called  crude  potashes.  It  is  mainly  used  in  the  manufacture  of 
glass  and  soap. 

Potassium  nitrate,  KNO3,  is  saltpetre,  an  important  ingredient  in 
gunpowder,  of  which  it  forms  about  three-fourths  the  weight.  Its 
use  here  and  in  fireworks  is  -due  to  the  readiness  with  which  it  gives 
up  its  oxygen. 

Potassium  chlorate,  KC1O3,  is,  like  saltpetre,  a  white,  crystalline 
salt,  largely  used  in  fireworks  and  matches  to  supply  oxygen.  It 
is  also  used,  in  medicine. 

Potassium  chloride,  KC1,  much  resembles  common  salt;  the 
bromide,  KBr,  is  a  valuable  medicine.  The  ferrocyariide,  yellow 
prussiate  of  potash,  forms  with  iron  (ferric)  salts  the  well-known 
Prussian  blue. 

Potassium  tartrate  is  "  cream  of  tartar." 


SODIUM. 

Symbol,  Na.  —  Atomic  weight,  23.  —  Specific  gravity,  0.972. 

Sodium  is  a  beautiful  crystalline  metal,  of  silver-white  appear- 
ance. It  fuses  at  97. 6°  C.,  volatilizes  at  a  red  heat,  and  greatly 
resembles  potassium  in  all  its  properties.  Sodium  never  occurs 
native,  but  in  combination  it  is  of  universal  occurrence.  Potassium 
and  sodium  correspond  very  closely  in  all  their  chemical  combina- 
tions, the  chemical  activity  of  the  latter  being,  however,  somewhat 
weaker  than  that  of  the  former. 

Sodium  hydroxide,  or  caustic  soda,  NaOH,  is  a  white,  fusible, 
deliquescent  solid,  very  soluble  in  water,  though  less  so  than 
caustic  potash.  It  is  a  powerful  alkali. 


SODIUM.  65 


The  most  commonly  occurring  salt  of  sodium  is  the  chloride, 
NaCl,  or  "  common  salt."  It  is  obtained  by  the  evaporation  of  sea- 
water,  the  water  of  salt  springs  and  wells,  and  is  also  mined  as 
rock  salt.  Common  salt  crystallizes  generally  in  cubes.  It  is  solu- 
ble in  2j  times  its  weight  of  water  at  15^°  C.  It  fuses  and  volatil- 
izes at  a  red  heat.  Hydrochloric  acid  is  made  by  distilling  sodium 
chloride  with  sulphuric  acid,  2  NaCl  +  H2SO4  =  Na2SO4  +  2  HCL 
Glauber's  salt  is  crystallized  sodium  sulphate,  Na2SO4,  10H2O. 
Soda-ash  is  more  or  less  pure  anhydrous,  or  dry,  sodium  carbonate, 
Na2CO3.  "Soda  crystals,"  or  "  washing-soda,"  is  crystallized 
sodium  carbonate,  Na2CO3 , 10  H2O.  Common  baking-soda  is  sodium 
bicarbonate,  NaHCOs.  (For  description  of  processes  of  manufac- 
turing soda-ash,  etc.,  see  Manufacture  of  Alkali.)  Borax  is  sodium 
biborate,  Na2B4O:,  10  H2O.  Borax  is  found  native  in  California.  It 
is  soluble  in  12  parts  of  cold,  and  in  one-half  part,  or  one-half  its 
weight  of  boiling  water.  Borax  when  heated  swells  up,  loses  its 
water  of  crystallization,  and  finally,  at  about  a  red  heat,  melts  to 
a  clear  glass.  It  is  of  great  value  as  a  flux  in  metal  working. 

Sodium  nitrate,  NaNO3,  is  found  native  in  Peru  and  Chili,  and 
is  imported  from  these  places  in  large  quantities.  It  has  very 
nearly  the  same  properties  as  saltpetre,  KNO3,  but  cannot  be  sub- 
stituted for  the  latter  in  gunpowder,  since  it  attracts  moisture. 
Saltpetre  is  made  from  sodium  nitrate  by  what  is  called  double 
decomposition  between  that  salt  and  potassium  chloride.  When 
solutions  of  the  two  salts  are  mixed  in  the  proper  proportions  an 
interchange  of  acids  and  bases  occurs,  and  potassium  nitrate  and 
sodium  chloride  result  — 

NaNO,  +  KC1  =  KNO,  +  NaCl. 

The  normal  salts  of  sodium  are  all  soluble  in  water,  with  the  single 
exception  of  pyr-antimonate  of  sodium,  Na2Sb2O7 ,  6  H2O. 

The  compounds  of  sodium  are  the  most  useful  in  the  variety  and 
extent  of  their  applications  of  any  of  the  salts  of  the  alkalis. 

Manufacture  of  Alkali.  —  The  manufacture  of  soda-ash  from 
common  salt,  by  the  Leblanc  process,  depends  primarily  upon  the 
following  reactions :  — 

Common  salt,    Sulphuric  acid.      Acid  podium  sulphate.    Hydrochloric  acid. 

(1)  NaCl  4-    H.S04     =       NaHSO4       +        HC1. 

Sodium  sulphate. 

(2)  KaCl  +    NaHS04=       Na^         +        HC1. 


66  GENERAL   CHEMISTRY. 

(3)  By  heating  sodium  sulphate,  Na^SO*,  with  carbon  in  the  form 
of  coal  and  with  chalk,  calcium  carbonate,  CaC08,  the  various  reactions 
shown  below  are  set  up,  which  result  in  the  production  of  black-ash, 
from  which  sodium  carbonate  may  be  extracted  by  lixiviation.  These 
phases  of  reaction  (3)  may  be  regarded  thus  — 

Carbon.  Sodium  sulphide.       Carbon  monoxide. 

(a)          SNa^  +  lOC        =  5Na2S       +       10  CO. 


Calcium  sulphide. 

(6)  5  Na2S  +  5  CaC03  =  5  Na2OO)i  +      5  CaS. 

Caustic  lime. 

(c)  2CaC03  +  2C         =2CaO         +       4  CO. 

Reactions  (1)  and  (2)  on.  page  65  are  carried  out  in  iron  pots, 
set  in  a  furnace,  and  containing  the  charge  of  salt,  upon  which 
the  sulphuric  acid  is  run.  The  torrents  of  hydrochloric  acid  gas 
which  are  evolved  pass  out  of  the  furnace  and  up  through  scrub- 
bers, or  towers,  filled  with  flints,  down  which  a  stream  of  water 
trickles.  The  gas  is  absorbed  by  the  water,  forming  commercial 
muriatic  acid,  which  flows  from  the  bottom  of  the  tower.  The 
sodium  sulphate,  or  salt  cake  as  it  is  technically  termed,  is  removed 
from  the  pots  and  made  up  into  what  is  called  black-ball,  with 
coal,  lime,  and  limestone  or  chalk.  This  mixture  is  furnaced,  and 
under  the  influence  of  heat  the  various  phases  of  reaction  (3) 
are  set  up,  and  black-ash,  yielding  in  different  works  from  23 
to  45  per  cent,  of  sodium  carbonate,  with  a  much  smaller  and 
varying  percentage  of  caustic  soda,  is  obtained.  The  carbonate 
and  caustic  are  removed  by  washing  the  black-ash  with  water, 
and  the  solution  is  either  subjected  to  minor  operations  to  purify 
the  subsequent  product,  or  is  run  down  at  once  to  obtain  the 
commercial  soda-ash.  For  the  preparation  of  caustic  soda  the 
black-ash  liquors  are  usually  treated  at  once  with  lime,  air  is 
blown  through  the  mixture  to  decompose  sulphides,  etc.,  and  the 
caustic  liquor  decanted  and  evaporated.  In  many  works  the 
caustic  is  produced  at  once  in  the  furnace  by  somewhat  increasing 
the  quantity  of  coal  added  to  the  mixture  of  salt  cake  and  lime- 
stone, and  lixiviating  the  ball-soda  at  once  with  water  at  50°. 

The  hydrochloric  or  muriatic  acid  obtained  in  reactions  (1)  and 
(2)  above  is  decomposed  as  described  under  Chlorine,  for  the 
manufacture  of  bleaching-powder,  or  more  rarely  of  potassium 
chlorate. 


SODIUM. 


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68  GENERAL   CHEMISTRY. 

A  large  and  increasing  quantity  of  high-grade  soda-ash  is  now 
manufactured  by  the  Solvay  or  ammoniacal  process,  which  depends 
upon  the  fact  that  if  common  salt  is  dissolved  in  ammonia  water, 
and  a  current  of  carbonic  acid  gas  passed  through  the  solution, 
ammonium  chloride  is  formed  and  sodium  bicarbonate  precipitated. 
The  bicarbonate  is  then  washed  free  from  the  solution,  and  upon 
ignition  yields  the  carbonate.  The  ammonia  is  recovered  by  heat- 
ing the  ammonium  chloride  with  lime,  the  chlorine  combining  with 
the  lime  to  form  calcium  chloride,  which  is  a  waste  product.  On 
account  of  this  loss  of  chlorine  no  bleaching-powder  is  made  by 
this  process. 

LITHIUM. 

Symbol,  Li.  — Atomic  weight,  7.  —Specific  gravity,  0.69. 

Lithium  is  a  white,  lustrous  metal,  discovered  by  Arf wedson  in 
1818.  It  is  the  lightest  solid  known,  being  only  about  one-half  as 
heavy  as  water.  It  is  fusible  at  180°  C.,  and  volatile  at  a  red  heat. 
It  occurs  as  chloride  in  many  mineral  springs,  and  as  silicate  or 
fluoride  in  not  a  few  minerals.  It  is  of  no  importance  other  than, 
as  a  medicinal  agent. 

O2ESIUM. 

Symbol,  Cs.  —  Atomic  weight,  133. 

RUBIDIUM. 

Symbol,  Kb.  —  Atomic  weight,  85.4. 

Both  these  metals  were  discovered  by  Bunsen  and  Kirchoff  in 
spring  waters  in  Hungary.  They  are  present  also  in  a  few  minerals. 
Traces  of  caesium  have  also  been  found  in  the  ashes  of  tobacco, 
beetroot,  coffee,  and  grapes.  Both  are  very  rare  metals,  and  form 
no  compounds  of  any  commercial  importance. 


AMMONIUM. 

Symbol,  NH4 .  —  Combining  weight,  18. 

Ammonium  (a  compound  of  hydrogen  and  nitrogen,  not  to  be 
confounded,  however,  with  ammonia,  NH3)  is  not  in  reality  a 
metal,  but  in  many  of 'its  combinations  so  nearly  plays  the  part  of  an 
alkali  metal,  and  its  compounds  are  so  similar  to  the  corresponding 


METALS  OF  THE  ALKALINE  EARTHS. 


compounds  of  potassium  and  sodium,  that  they  may  be  best  con- 
sidered here. 

Ammonium  unites  with  water  to  form  ammonium  hydrate  or 
hydroxide,  NH4OH,  the  common  ammonia  water,  which  possesses 
all  the  alkaline  properties,  though  in  less  degree,  of  a  solution  of 
potassium  or  sodium  hydrate. 

It  unites  with  acids  to  form  ammonium  sulphate  (NH4)2SO4, 
chloride  (NH4)C1,  carbonate  (NH4)COa,  etc.,  strictly  analogous  to 
the  corresponding  salts  of  the  alkali  metals. 

Ammonium  is  often  carelessly  mistaken  for  hydrogen  nitride,  or 
ammonia,  NH3,  but  it  should  never  be,  as  it  is  entirely  distinct. 
Ammonia,  NH3,  never  enters  into  combination  with  acids  to  form 
salts,  these  compounds  always  being  formed  from  ammonium, 
NH4.  Ammonia  by  contact  with  water  is  changed  into  ammonium 
hydroxide  (NH4)OH,  which  then  may  perform  all  the  functions  of 
any  other  alkaline  hydroxide. 

Ammonium,  NH4 ,  is  a  good  type  of  what  is  called  a  Radicle  ;  that 
is,  an  unsaturated  group  of  atoms,  which  in  combination  plays  the 
part  of  a  single  atom.  The  number  of  such  groups  or  radicles 
known  to  organic  chemistry  is  very  large,  and  in  many  cases,  by 
the  coalescence  of  two  groups  of  the  same  kind,  a  stable  molecule 
is  formed,  so  that  the  radicle  can  exist  in  the  free  state.  Cyanogen, 
—  C  ~  N,  is  such  an  organic  radicle,  the  molecule  of  free  cyanogen 
being  N  s  C  -  C  s  N. 


METALS   OF  THE  ALKALINE  EARTHS. 

Barium :         Symbol,  Ba.  —  Atomic  weight,  137.    —  Specific  gravity.  4.000. 
Strontium:   Symbol,  Sr.  —      "  "        87.5.—      "  "         2.540. 

Calcium :       Symbol,  Ca.—      "  "        40.    —      "  "         1.578. 

These  metals  all  decompose  water  at  the  ordinary  temperature. 
They  form  oxides  of  an  earthy  nature.  These  combine  with  water 
(slake),  forming  hydroxides,  which  dissolve  somewhat  in  water, 
forming  alkaline  solutions.  All  are  strong  bases.  Theirccarbon- 
ates  are  insoluble.  Their  bicarbonates  and  most  of  their  other 
salts  are  soluble  in  water.  One  atom  of  each  can  replace  two 
atoms  of  acid  hydrogen. 


70  GENERAL   CHEMISTRY. 

BARIUM. 

Symbol,  Ba.  —  Atomic  weight,  137.  —  Specific  gravity,  4.000. 

Barium  is  a  silver-white  metal,  which  melts  below  a  red  heat 
and  oxidizes  readily.  It  may  be  obtained  by  the  electrolysis  of 
fused  barium  chloride. 

Barium  oxide  or  caustic  baryta  is  obtained  by  calcining  barium 
carbonate,  BaCO3,  at  a  red  heat.  It  combines  eagerly  with  water, 
with  the  development  of  much  heat,  and  forms  barium  hydroxide 
or  hydrate,  BaH2O2 .  The  hydroxide  is  soluble  in  20  parts  of  cold 
or  two  parts  of  boiling  water. 

The  solution  is  strongly  alkaline.  Barium  hydrate  and  all  the 
soluble  salts  of  barium  are  very  poisonous,  their  antidotes  being 
sodium  or  magnesium  sulphate. 

The  soluble  salts  of  barium  are  the  chloride,  BaCl2 , 2  H2O,  nitrate, 
BaN«Oa,  chlorate,  BaCl2O6,  the  acetate,  BaC4H«O4,  3  H2O,  and  the 
thiosulphate,  BaS2O8,HxO.  Barium  sulphate,  BaSO4,  is  insoluble. 
It  is  frequently  employed  as  an  adulterant  of  white  lead  in  paint, 
and  to  some  extent  as  a  filler  in  paper.  It  is  found  native  as 
"  Heavy  spar."  Barium  carbonate  is  also  found  native  as  "  With- 
erite."  The  soluble  salts  of  barium  impart  a  green  color  to  the 
colorless  flame  of  alcohol  or  of  the  Bunsen  gas-burner. 

Barium  oxide,  when  heated  in  a  current  of  dry  air,  takes  on  a 
second  atom  of  oxygen,  the  peroxide,  BaO2,  being  formed.  At  a 
still  higher  temperature  the  peroxide  is  reduced  to  the  original 
barium  oxide,  BaO,  oxygen  being  at  the  same  time  liberated.  This 
reaction  has  been  made  use  of  in  the  preparation  of  oxygen  on  the 
large  scale,  the  barium  oxide  being  alternately  brought  to  the 
lower  and  higher  temperature  in  retorts,  which  are  first  connected 
with  a  source  of  air,  and  then  with  gas-holders.  The  Brins,  who 
have  developed  the  process  in  the  commercial  way,  prepare  a  solu- 
tion for  bleaching  paper  stock  by  saturating  hydrochloric  acid  with 
oxygen.  . 

Barium  peroxide  is  also  interesting  as  furnishing  a  means  for 
preparing  hydrogen  peroxide,  H2O2.  Thus,  when  barium  peroxide 
is  treated  with  water  and  hydrochloric  acid,  barium  chloride  and 
hydrogen  peroxide  are  formed  — 

Ba02  +  2  HC1  =  BaCls  +  H2O2, 
both  products  remaining  in  solution. 


CALCIUM.  71 


When  sulphuric  acid  is  employed  barium  sulphate  is  precipi- 
tated, and  a  pure  solution  of  hydrogen  peroxide  in  water  is  obtained, 
which  may  be  used  for  bleaching  or  other  purposes. 

STRONTIUM. 

Symbol,  Sr.  — Atomic  weight,  87.5.  — Specific  gravity,  2.54. 

Strontium  is  a  yellow  metal,  somewhat  harder  than  lead.  In  its 
properties  and  reactions  it  is  very  similar  to  barium.  Its  hydrox- 
ide, SrH2O2 ,  is  somewhat  less  soluble  than  barium  hydroxide,  while 
most  of  its  compounds  are  more  soluble  than  the  corresponding 
barium  compounds.  Strontium  compounds  impart  a  crimson  color 
to  flame.  They  find  their  chief  employment  in  the  manufacture 
of  "red  fire."  The  hydroxide  forms  a  comparatively  insoluble 
compound  with  sugar  (sucrose),  and  hence  affords  a  means  of 
separating  the  latter  from  the  uncrystallizable  sugar  of  molasses. 

CALCIUM. 

Symbol,  Ca.  —Atomic  weight,  40.  —  Specific  gravity,  1.578. 

Calcium  is  never  found  native,  but  its  compounds,  especially  the 
carbonate,  silicate,  and  phosphate,  are  widely  distributed,  and  are 
of  great  use  and  value.  The  metal  calcium  is  prepared  with  con- 
siderable difficulty,  and  is  of  no  importance  as  a  metal.  It  is  of  a 
light-yellow  color,  about  as  hard  as  gold ;  is  malleable  and  ductile. 
It  tarnishes  slowly  in  dry  air,  and  decomposes  water  rapidly  at  the 
ordinary  temperature.  When  heated  in  oxygen  it  burns  with  a 
magnificent  rose-red  flame.  Like  barium,  it  forms  two  oxides,  CaO 
and  CaO2 ,  the  former  only  being  of  importance.  Calcium  oxide, 
CaO,  is  ordinary  "  quicklime."  It  is  a  white,  caustic,  earthy  sub- 
stance, infusible  when  pure.  When  heated  in  the  oxyhydrogen 
flame  it  glows  with  an  intense  white  light,  rivalling  the  light  of 
the  electric  arc.  Calcium  oxide  combines  with  water  with  the 
development  of  great  heat,  and  flakes  "  into  calcinm  hydroxide 
or  hydrate,  CaH2O2.  The  latter  substance  is  a  strongly  alkaline 
base,  soluble  in  TOO  times  its  weight  of  cold  water,  but  much  less 
soluble  in  boiling  water. 

A  clear  saturated  solution  of  calcium  hydrate  is '  the  lime-water 
of  pharmacy,  and  water  containing  more  CaH2O,  than  it  is  able  to 
dissolve  is  called  milk  of  lime.  Calcium  hydroxide  forms  the  basis 


72  GENERAL   CHEMISTRY. 

of  mortars  and  cements.  The  hardening  or  setting  of  mortar  js 
brought  about  by  the  combination  of  the  lime  with  the  carbonic 
acid  of  the  atmosphere  to  form  carbonate  of  lime,  aided  by  the 
silica  of  the  sand  used,  which  forms  silicate  of  lime  to  a  small 
extent, 

"  Hydraulic  lime "  is  lime  which  contains  free  soluble  silica. 
Such  lime,  when  moistened,  first  slakes  and  then  in  a  short  time 
sets  to  a  hard  mass  through  the  combination  of  the  lime  with  the 
soluble  silica,  forming  stone. 

This  setting  will  take  place  even  under  water.  Hydraulic  lime 
is  employed  in  the  manufacture  of  Portland  cement,  and  gives  the 
cement  its  valuable  properties.  Calcium  hydrate  is  capable  of 
many  useful  applications,  as  in  causticizing  soda  (compare  Soda- 
ash),  preparing  indigo  for  coloring,  as  a  " base"  in  the  sulphite 
pulp  process,  and  in  the  manufacture  of  bleaching-powder,  etc. 

Calcium  oxide,  CaO,  is  prepared  by  calcining,  or  burning,  lime- 
stone, calcium  carbonate,  CaCO3,  in  a  kiln.  The  heat  decomposes 
the  calcium  carbonate,  driving  off  the  carbonic  acid  as  gas,  CO2, 
while  the  stone  is  changed  into  quicklime,  CaO.  Marble  and 
chalk  are  nearly  pure  calcium  carbonate,  while  ordinary  limestone 
contains  varying  amounts  of  magnesia,  iron  oxide,  alumina,  silica, 
etc.  A  lime  for  building  purposes  may  contain  quite  considerable 
amounts  of  impurities  other  than  magnesia  without  seriously  injur- 
ing it.  On  the  other  hand,  a  lime  for  sulphite  liquor  making  may 
contain  almost  any  amount  of  magnesia,  though  moderate  amounts 
of  other  impurities  are  objectionable ;  while  lime  intended  for  the 
manufacture  of  bleaching-powder  must  be  very  nearly  pure  CaO. 

Calcium  hydrate  is  a  strong  base.  Some  of  the  salts  of  calcium 
are  extremely  soluble  in  water,  as  the  chloride,  CaCl2,  nitrate, 
€aN2O6,  and  the  chlorate,  CaCLO6.  A  larger  number  are  moder- 
ately soluble,  as  the  hypochlorite,  CaCl2O2,  sulphate,  CaSO4,  etc.; 
while  not  a  few  are  almost  absolutely  insoluble,  as  the  carbonate, 
CaCO3,  the  sulphite,  CaSO3,  and  the  phosphate,  Ca3P2O8.  In  some 
cases  the  insoluble  salts  of  calcium  may  combine  with  a  second 
equivalent  of  the  acid,  as  the  carbonate,  to  form  bicarbonate,  and 
the  sulphite  to  form  bisulphite,  the  latter  salts  being  largely  solu- 
ble. The  so-called  "  hard  "  waters  often  contain  calcium  bicarbon- 
ate. In  this  case  boiling  removes  the  "  hard  "  quality,  the  second 
equivalent  of  carbonic  acid  being  liberated  by  the  heat,  and  the 
lime  precipitated  as  the  insoluble  carbonate.  Bisulphite  of  lime 


MAGNESIUM.  78 


solutions  are  decomposed  in  a  similar  way  by  boiling,  with  the  pre- 
cipitation of  calcium  sulphite.  Other  soluble  salts  of  lime  produce 
44  hardness  "  in  water,  which  remains  after  boiling,  and  hence  is 
called  "permanent  hardness." 

Selenite,  gypsum,  anhydrite,  and  alabaster  are  all  different  nat- 
ural forms  of  calcium  sulphate,  CaSO4.  44 Pearl  hardening,"  "pearl 
pulp,"  and  44  crown  filler "  are  artificial  sulphate  of  lime,  prepared 
for  xise  as  4i  fillers  "  in  paper.  Crystallized  sulphate  of  lime,  GaSO4, 
2  H2O,  is  soluble  in  400  times  its  weight  of  water,  or  one  pound  in 
about  48  gallons,  at  the  ordinary  temperature.  It  is  less  soluble  in 
hot  water.  At  100°  C.  sulphate  of  lime  loses  three-fourtha  of  its 
water  of  crystallization ;  at  about  260°  C.  still  more  is  lost,  and  it 
becomes  plaster  of  Paris.  When  the  latter  is  moistened  it  again 
combines  with  water,  increases  in  bulk,  and  sets  to  a  hard  mass.  If 
heated  much  above  260°  C.,  plaster  of  Paris  recombines  with  water 
only  very  slowly. 

Calcium  phosphate,  Ca3P2O8,  forms  the  greater  part  of  bone.  It 
is  also  found  native  in  Canada  as  apatite,  and  in  South  Carolina  as 
44  phosphate  rock."  Coprolites,  supposed  to  be  the  fossil  excreta  of 
prehistoric  animals,  are  nearly  pure  phosphate  of  calcium.  These 
are  all  largely  used  in  the  manufacture  of  artificial  fertilizers  or 
superphosphates . 

THE  MAGNESIUM  GROUP. 

Magnesium :  Symbol,  Mg.  —  Atomic  weight,  24.    —  Specific  gravity,  1. 743.      Melting 

point. 

Zinc:  Symbol,  Zn.  —      "  "      65.2.—       "          "      7. 146.  — 412° C. 

Cadmium:      Symbol,  Cd.—      "  "    112.    —       "          "      8.604.— 228° C. 

Olucinum:      Symbol,  Be.  —      "  "       9.8.—       "          "      2. 100.  —  900C C. 

These  metals  all  have  a  valency  of  2.  They  all  burn  when 
heated  in  the  air,  and  are  all  volatile.  They  each  form  but  a 
single  oxide.  Their  carbonates  are  insoluble  in  water,  but  are 
dissolved  by  solution  of  ammonium  carbonate.  The  metals  of  this 
group  decompose  water  only  very  slightly.  They  dissolve  in 
hydrochloric  acid  with  evolution  of  hydrogen. 

MAGNESIUM. 

Symbol,  Mg.  — Atomic  weight,  24.  —Specific  gravity,  1.743. 

Magnesium  is  a  white  metal,  malleable  and  ductile.  It  is  never 
found  native.  It  oxidizes  slowly  in  damp  air.  It  burns  rapidly 


74  GENERAL   CHEMISTRY. 

when  heated  in  the  air,  with  a  brilliant  white  light,  which  may  be 
employed  instead  of  sunlight  in  photography.  Magnesium  oxide 
or  magnesia,  MgO,  is  formed  when  magnesium  is  burned.  It  is 
prepared  on  a  large  scale  by  calcining  carbonate  of  magnesium, 
MgCO8,  in  the  same  manner  as  limestone  is  calcined.  Magnesia 
resembles  lime,  but  its  hydroxide,  MgH2O2,  is  much  less  soluble 
than  hydrate  of  lime.  It  forms  combinations  similar  to  the  corre- 
sponding lime  compounds,  but  its  basic  properties  are  less  strong 
than  those  of  lime,  and  most  of  its  compounds  are  largely  soluble 
in  water.  Epsom  salts  is  magnesium  sulphate,  MgSO4,  7  aq.1  This 
is  soluble  in  three  times  its  weight  of  water.  Many  of  the  salts  of 
magnesium  are  of  importance  in  pharmacy.  Magnesia  forms  the 
base  for  the  manufacture  of  bisulphite  liquor  in  the  Ekman  proc- 
ess for  the  manufacture  of  pulp*  Silicate  of  magnesium,  with 
small  proportions  of  other  metallic  silicates,  forms  a  very  impor- 
tant class  of  minerals.  Meerschaum,  talc,  soapstone,  serpentine, 
and  asbestos  are  mainly  magnesium  silicates. 


ZING. 

Symbol,  Zn. — Atomic  weight,  65.2,  —  Specific  gravity,  7.146. 

Zinc  is  a  bluish  white,  hard,  lustrous  metal.  It  is  rarely  found 
native,  the  best  ore  being  calamine,  zinc  carbonate,  ZnCO8.  Zinc 
is  brittle  at  low  temperatures,  but  becomes  malleable  and  ductile 
'between  100°  and  150°  C.  It  melts  at  412°  C.,  and  boils  at  1040°  C. 
It  oxidizes  very  slowly  in  the  air,  and  hence  is  employed  for  coat- 
ing or  "  galvanizing  "  iron  to  protect  it  from  rust.  .It  is  readily 
attacked  by  chlorine  and  all  the  mineral  acids,  and  dissolved  by 
them.  Zinc  forms  the  electro-positive  element  in  most  electric 
batteries,  the  wire  leading  from  it  forming  the  negative  pole. 
It  is  capable  of  replacing  most  other  metals  in.  solution,  itself 
being  dissolved ;  while  the  metal  originally  in  the  solution  is,  at 
the  same  time,  deposited  in  the  metallic  state.  Zinc  heated  in  the 
air  burns  with  a  greenish  blue  flame,  forming  oxide  of  zinc,  ZnO. 
This  is  yellow  while  hot,  but  on  cooling  becomes  white.  Zinc 
hydroxide  is  a  white,  gelatinous  substance,  insoluble  in  water,  but 

1  The  abbreviation  Aq.  for  aqua  (water)  is  frequently  used  to  represent  a  mole- 
cule, H,O,  of  water  which  is  present  as  such  in  association  with  some  other  mole- 
cule. 


GLUCINUM.  75 


dissolved  by  solution  of  potash  or  ammonia.  Metallic  zinc  is 
obtained  from  the  oxide  by  heating  with  charcoal  — 

2ZnO-KC=2Zn  +  C02. 

Chloride  of  zinc,  ZnCl2,  dissolved  in  water,  forms  "  Burnett's  dis- 
infecting solution  "  of  pharmacy.  Cellulose  or  paper  treated  with 
a  strong  solution  of  zinc  chloride  is  changed  into  a  transparent, 
parchment-like  substance,  vegetable  parchment.  Sulphate  of  zinc, 
44  white  vitriol,"  ZnSO4,  7  aq.,  is  employed  in  calico-printing  as  a 
mordant.  Zinc  carbonate  or  "  zinc  white  "  finds  considerable  use 
as  a  substitute  for  white  lead  in  paint. 


CADMIUM. 

Symbol,  Cd.  — Atomic  weight,  112.  — Specific  gravity,  8.6. 

Cadmium  is  a  metal  much  resembling  zinc  and  also  tin.  It 
accompanies  zinc  in  many  of  its  ores.  It  melts  at  228°  C.,  boils  at 
860°  C.,  and  is  more  volatile  than  zinc.  It  tarnishes  but  little  in 
the  air,  but  when  strongly  heated  burns  to  cadmium  oxide,  CdO. 
Its  salts  resemble  the  corresponding  salts  of  zinc,  but  the  metal  is 
of  little  importance  either  in  the  metallic  state  or  in  combination. 

GLUCINUM. 

Symbol,  Be.  — -  Atomic  weight,  9.3.  —  Specific  gravity,  2.1. 

Also  called  beryllium  from  its  being  the  principal  constituent  of 
the  beryl.  It  is  a  white,  malleable  metal.  Called  glucinum  from 
the  Greek  word  J\VKV^  meaning  sweet,  on  account  of  the  sweet 
taste  of  solutions  of  its  salts.  Its  salts  resemble  both  those  of  zinc 
and  aluminum,  but  are  of  no  importance.  The  emerald  is  a  double 
silicate  of  beryllium  and  aluminum. 


76  GENERAL   CHEMISTRY. 


THE  EARTH  METALS. 


Aluminum  : 

Symbol, 

Al.  —  Atomic  weight,  27.4. 

Yttrium: 

Symbol, 

Y  —       * 

92.0. 

Erbium  : 

Symbol, 

E.  —      -* 

1       168.9. 

Lanthanum  : 

Symbol, 

La.—      4 

«       139.0. 

Didymium  : 

Symbol, 

D.  —       * 

'       144.7. 

Cerium  : 

Symbol, 

Ce.—      '               '       138.0. 

These  metals  are  all  capable  of  replacing  three  atoms  of  hydrogen 
in  combination.  Their  oxides  are  earths,  and  are  reduced  to  the 
metallic  state  only  with  great  difficulty.  From  solutions  of  their 
salts  ammonium  sulphide  precipitates  the  metal  as  hydroxide. 

ALUMINUM. 

Symbol,  Al.  —  Atomic  weight,  27.4.  —  Specific  gravity,  2.6. 

Aluminum  is  a  bluish  white,  malleable,  and  ductile  metal,  first 
prepared  by  Wohler  in  1827.  It  is  a  good  conductor  of  electricity, 
and  is  very  sonorous.  It  fuses  at  about  450°  C.  It  does  not 
tarnish  in  the  ain,  but  when  heated  in  oxygen  it  burns  with  a 
bluish  white  light,  forming  the  oxide,  A12O8 .  It  dissolves  in  acids, 
with  the  exception  of  nitric  acid,  with  moderate  facility.  Solutions 
of  potassium  and  sodium  hydroxides  also  dissolve  it  readily  with 
the  liberation  of  FL.  The  metal  is  never  native,  but  the  oxide  and 
silicate  are  found  in  abundance,  the  latter  forming  the  principal 
part  of  clay.  Corundum  and  emery  are  native  Al}Qs . 

The  sapphire  and  ruby  are  also  oxide  of  aluminum,  tinted  with 
small  amounts  of  other  metallic  oxides.  Bauxite  is  a  hydrous 
oxide  of  aluminum,  containing  more  or  less  iron  oxide.  Aluminum 
possesses  properties  which  would  render  it  a  very  valuable  metal 
for  many  industrial  purposes.  The  difficulty,  of  reducing  its  ores 
has,  however,  up  to  the  present  rendered  its  cost  too  high  to  admit 
of  its  application  to  any  but  a  few  special  purposes. 

The  price  of  the  metal  has,  however,  been  reduced  about  one- 
half  within  a  couple  of  years,  but  it  still  remains  at  about  $0.65  per 
pound. 

The  salts  of  aluminum  are  easily  prepared  from  many  of  its 
natural  compounds,  and  are  of  great  value,  especially  to  the  paper 
manufacturer. 


ALUMINUM.  77 


Aluminum  hydroxide,  A12O3,  3  H2O,  is  precipitated  as  a  nearly 
colorless,  translucent  jelly  when  a  solution  of  any  aluminum  com- 
pound is  mixed  with  a  hydrate  of  an  alkali,  or  alkali-earth  metal. 
Hydrate  of  aluminum,  on  strong  ignition,  loses  its  combined 
water,  and  is  converted  into  the  oxide  or  alumina,  A12O3. 
Hydrate  of  aluminum  or  aluminum  hydroxide  is  a  moderately 
strong  base.  It  is  entirely  insoluble  in  water,  but  dissolves  readily 
in  acids  to  form  the  corresponding  salts.  Aluminum  chloride, 
AlgClg,  is  not  of  much  importance.  Aluminum  acetate  is  of  con- 
siderable use  as  a  mordant  for  fixing  the  colors,  and  obtaining 
different  shades  in  dyeing  arid  calico-printing.  By  far  the  most 
important  of  the  alumina  compounds  are  the  alums.  Alums, 
properly  so  called,  are  the  crystallized  double  sulphates  of 
aluminum  and  an  alkali.  Tims  potash  alum  is  K2A12  4  SO4,  24  aq>, 
and  contains  10.92  per  cent,  of  alumina,  A12O3,  and  45.51  per  cent, 
of  combined  water.  Soda  alum  is  Na2Al2  4  SO4,  24  aq.,  and  con- 
tains 11.23  per  cent,  of  alumina,  and  47.11  per  cent,  of  combined 
water.  Ammonium  alum  is  (NH4)2A12  4  SO4,  24  aq.,  and  contains 
11.35  per  cent,  of  alumina  and  47.63  per  cent,  of  combined  water. 
These  percentages,  of  course,  represent  what  the  chemically  pure 
crystals  of  these  alums  -contain,  and  not  the  "  commercially  pure  " 
article.  Sulphate  of  alumina,  A12  3SO4,  18  aq.,  is  largely  used  in 
paper-making  instead  of  true  alum,  since  in  the  partly  dried  form 
in  which  it  appears  in  market  it  is  stronger  in  alumina  than  the 
true  alums,  and  at  the  same  time  cheaper.  This  may  contain 
from  about  15  to  about  30  per  cent,  of  alumina,  according  to  the 
completeness  with  which  the  combined  water  has  been  driven  off 
in  the  manufacture. 

Among  the  insoluble  salts  of  aluminum  may  be  mentioned 
cryolite,  the  double  fluoride  of  aluminum,  and  sodium,  which  is 
found  in  large  quantities  in  Greenland,  and  is  employed  as  a  source 
of  alumina  in  alum  manufacture ;  clay  (silicate  of  alumina)  and 
bauxite  (hydrate  of  alumina)  are  also  employed  in  the  manufacture 
of  aluin  and  aluminum  sulphate. 

The  turquoise  is  a  hydrous  phosphate  of  aluminum. 

Manufacture  of  Alum.  —  As  already  indicated,  the  term  "alum" 
in  paper-making  has  come  to  be  almost  entirely  restricted  to  sulr 
phate  of  aluminum,  or  concentrated  alum*  as  it  is  often  called. 
This  material  is  in  this  country  generally  prepared  from  bauxite. 
The  pulverized  mineral  is  added  to  sulphuric  acid  of  50°  B.,  con- 


78  GENERAL   CHEMISTRY. 

tained  in  lead  tanks.  The  reaction  is  very  violent,  much  heat  is 
developed,  and  considerable  frothing  occurs.  After  the  mixture 
has  cooled  down  it  is  diluted  with  water,  and  allowed  to  stand  to 
deposit  silica  and  other  impurities.  The  clear  liquor  is  decanted 
and  run  into  tanks  heated  by  steam  passing  through  coils  of  lead 
pipe.  The  evaporation  is  continued  until  a  portion  of  the  liquor 
taken  up  on  a  stick  or  rod  solidifies  in  cooling.  The  concentrated 
material  is  then  run  off  upon  a  stone  table,  where  it  solidifies,  and 
is  subsequently  broken  up  and  packed.  Zinc  is  .sometimes  added 
while  the  alum  is  in  the  liquid  state,  and  by  its  action  while  dis- 
solving nascent  hydrogen  is  liberated  and  reduces  any  iron 
present  to  the  ferrous  state,  thereby  improving  the  color  of  the 
product.  If  sodium  bicarbonate  is  added  just  before  the  mass  is 
poured,  the  liberated  carbonic  acid  produces  the  structure  found  in 
porous  alum. 

In  order  to  produce  true  potash  or  ammonia  alum,  sulphate  of 
potash  or  sulphate  of  ammonia  is  added  to  the  clear  liquor  decanted 
after  treatment  of  the  bauxifee  with  acid.  The  concentration  is 
not  carried  so  far  as  in  the  manufacture  of  sulphate  of  alumina,  and 
the  alum  solution  is  run  into  wooden  tanks  to  crystallize.  The 
tanks  are  then  knocked  down  to  obtain  the  crystals. 

When  clay  is  used  as  the  source  of  alumina,  it  is  moderately 
heated  to  drive  off  water,  convert  the  iron  to  oxide,  and  render  the 
whole  mass  as  porous  as  possible. 

The  powdered  clay  is  added  gradually  to  sulphuric  acid  of 
50°  B.,  and  the  whole  heated  nearly  to  boiling  in  lead  tanks.  The 
mixture  gradually  thickens,  and  is  run  out  into  iron  pans  to 
solidify.  The  sulphate  of  alumina  is  washed  out  with  water,  and 
cleared  by  standing.  The  liquor  is  then  treated  in  the  same  man- 
ner as  that  obtained  from  bauxite. 

A  large  quantity  of  alum  for  paper-makers'  use  is  made  in  this 
country  from  cryolite.  By  ignition  of  cryolite  with  limestone, 
aluminate  of  soda  and  calcium  fluoride  are  formed.  The  former  is 
soluble  in  water,  and  may  be  washed  out.  From  this  solution 
carbonic  acid  gas  precipitates  the  alumina,  which  is  then  dissolved 
in  sulphuric  acid  to  form  sulphate  of  alumina.  Another  method  is 
to  boil  the  cryolite  with  milk  of  lime.  Aluminate  of  soda  and 
calcium  fluoride  are  formed,  and  upon  addition  of  a  further  quantity 
of  powdered  cryolite  the  alumina  is  precipitated  and  treated  with 
acid  as  before. 


THE  IRON  GROUP.  79 


In  England  alum  is  largely  manufactured  from  the  bituminous 
shale  containing  iron  pyrites  and  found  lying  above  the  coal 
measures.  The  shale  is  heaped  up  and  roasted,  by  which  operation 
the  pyrites  are  converted  into  ferrous  sulphate  and  sulphuric  acid, 
both  of  which  react  upon  the  clay,  forming  sulphate  of  alumina: 
This  may  either  be  dissolved  out  with  water,  or  the  roasted 
material  may  be  transferred  to  covered  pans  and  heated  to  about 
110°  for  two  days  with  sulphuric  acid  of  specific  gravity  1.35,  while 
ammonia  gas  is  passed  into  the  mixture  for  the  production  of 
ammonia  alum.  Potassium  sulphate  or  chloride,  or  more  often  a 
mixture  of  both,  added  to  the  lye  from  the  roasted  shale  yields 
potash  alum. 

YTTRIUM, 

Erbium,  lanthanum,  and  didymium  are  all  rare  metals,  found 
principally  in  Sweden.  They  never  occur  native.  None  of  their 
compounds  have  any  industrial  importance. 

CERIUM 

Is  a  little-known  metal  discovered  by  Klaproth  in  1803.  It  forms 
two  basic  oxides,  Ce2O3  and  CeO2,  and  consequently  two  classes  of 
salts,  eerie  and  cerous  respectively.  Cerium  oxalate  forms  a 
medicinal  agent  of  some  importance.  Apart  from  this  use  cerium 
is  of  no  industrial  importance. 


THE  IRON  GROUP. 
Iron  (Ferrum}  :  Symbol,  Fe.  — Atomic  weight,    66. 


Manganese :  Symbol,  Mn.  — 

Chromium  :  Symbol,  Cr.  — 

Cobalt:  Symbol,  Co.— 

Nickel :  Symbol,  Ni.  — . 

Uranium :  Symbol ,   U.  — 


55. 
52.2. 

68.8. 
58.8. 
120. 


This  group  includes  the  distinctively  magnetic  metals,  and  also 
non-magnetic  uranium.  These  metals  all  decompose  water  at  a 
red  heat.  Hydrogen  sulphide  does  not  precipitate  them  from  their 
dightly  add  solutions , 


80  GENERAL   CHEMISTRY. 

IRON  (Ferrum). 
Symbol,  Fe.  —  Atomic  weight,  56.  —  Specific  gravity,  7.844. 

Iron  very  rarely  occurs  native.  It  is  sometimes  present  in  the 
metallic  state  in  meteorites,  and  is  found  in  a  mica  slate  at  Canaan, 
Connecticut.  Pure  iron  is  an  almost  silver-white  metal,  malleable, 
ductile,  and  very  tenacious.  It  is  the  most  magnetic  of  all  sub- 
stances. It  remains  unchanged  in  dry  air,  and  when  immersed  irr 
pure  water.  In  damp  air  it  rusts  or  oxidizes.  Heated  in  oxygen, 
it  burns  with  vivid  incandescence,  forming  the  magnetic  oxide, 
Fe3O4.  Dilute  sulphuric  and  hydrochloric  acids  dissolve  it  readily 
with  evolution  of  hydrogen,  forming  protosulphate,  FeSO4,  and 
protochloride  of  iron,  FeCl2,  respectively.  Dilute  nitric  acid  also 
dissolves  it,  but  the  strong  acid  not  only  fails  to  dissolve  it  but 
renders  it  "passive,"  or  incapable  of  being  acted  upon  by  other 
acids,  until,  by  appropriate  means,  its  passive  condition  is  altered. 
Bar  iron,  the  purest  commercial  form,  contains  from  0.2  to  0.4  per 
cent,  of  carbon.  At  a  white  heat  it  softens,  and  may  be  welded  by 
hammering  or  by  strong  pressure.  In  electric  welding  a  small 
portion  of  the  iron  is  brought  to  a  white  heat  by  the  concentration 
on  it  of  a  very  powerful  electric  current,  and  the  two  surfaces  are 
united  by  strong  pressure.  Iron  melts  at  about  1530°  C. 

The  chief  ores  of  iron,  in  the  order  of  their  value,  are  magnetic 
iron  ore  or  magnetite,  Fe  O4,  which  occurs  both  massive  and  crystal- 
line, and  from  which  the  purest  iron  is  made  by  reduction  of  the  ore 
with  charcoal  alone ;  "  specular  "iron  ore,  Fe2O3 ;  and  red  haematite, 
2  Fe2O3,  3  aq.  This  last  occurs  in  two  forms,  fibrous  and  compact. 
By  roasting  it  loses  its  water  of  combination  and  becomes  Fe2O3, 
which  is  then  readily  reduced  to  iron  by  coal. 

"  Spathic  "  iron  ore,  carbonate  of  iron,  FeCO8,  occurs  in  yellow- 
ish crystals,  and  also  massive.  By  roasting,  carbonic  anhydride, 
CO2,  is  driven  off  and  the  FeO  oxidized  to  Fe2O3,  **  Clay  iron* 
stone  "  is  the  chief  ore  of  Great  Britain,  It  is  an  impure  carbonate 
of  iron  and  is  reduced  in  the  blast  furnace.  Blast  furnace  treat- 
ment is  in  outline  as  follows  :  The  ore  is  mixed  with  limestone  and 
small  coal  and  charged  into  the  top  of  the  furnace,  the  fires  of 
which  are  urged  by  a  strong  blast  of  air.  The  ore  and  the  lime- 
stone first  roast  in  the  cooler  portions  of  the  furnace,  and  become 
Fe,O3  and  CaO.  As  the  mass  sinks  down  the  lime  and  silica  of  the 
ore  unite  to  form  a  fusible  slag,  while  the  coal,  at  the  high  tempera- 


IRON  (FERRUW.  81 


ture,  burns  at  the  expense  of  the  oxygen  of  the  Fe2O3,  reducing  the 
latter  to  Fe,  which  sinks  to  the  bottom  of  the  furnace  in  a  fluid 
state,  and  is  drawn  off  from  time  to  time  by  the  removal  of  a  plug 
and  allowed  to  flow  into  furrows  in  a  bed  of  dry  sand  to  cool. 
These  bars  when  broken  up  form  "  pig  iron." 

There  are  many  minor  reactions  taking  place  all  the  while  in  the 
furnace,  which  we  have  not  space  to  notice  here.  "  Pig  iron  " 
contains  from  1  per  cent,  or  less  to  5  per  cent,  and  even  more  of 
carbon,  partly  or  wholly  combined  with  the  iron,  as  well  as  small 
amounts  of  sulphide  and  phosphide  of  iron.  These  must  be 
removed  by  different  processes  of  refining,  in  order  to  obtain 
"  wrought  iron."  The  presence  in  cast  iron  of  a  small  amount  of 
sulphide  or  arsenide  renders  it  "  hot  short,"  or  brittle  at  a  red  heat, 
while  a  small  amount  of  phosphide  renders  it  brittle  at  the  ordinary 
temperature,  or  "cold  short."  Steel  contains  from  0.7  to  1.7  per 
cent,  of  combined  carbon,  which  gives  it  its  special  properties. 

Iron  forms  four  oxides,  two  of  them,  FeO,  the  protoxide,  and 
Fe2O3,  the  sesquioxide,  being  basic ;  Fe3O4,  magnetic  oxide,  having 
neither  basic  nor  acid  properties,  and  consequently  forming  no 
compounds ;  and  FeO2,  an  acid  oxide.  The  last,  however,  can- 
not be  isolated,  since  when  freed  from  combination  it  immedi- 
ately evolves  oxygen  and  deposits  ferric  hydrate.  Ferrous  oxide, 
FeO,  is  very  unstable,  both  in  its  free  state  and  in  most  of  its 
compounds,  absorbing  oxygen  very  readily  and  passing  into  the 
ferric  state.  Most  of  the  ferrous  salts  are  soluble  in  water. 
Ferrous  sulphate,  "green  vitriol,"  FeSO4,  7aq,,  is  also  commercially 
called  "  copperas."  It  takes  this  name  from  the  fact  of  its  becom- 
ing reddish  brown,  coppery,  on  exposure  to  the  air.  It  is  a  sea- 
green,  crystalline  substance,  very  soluble  in  water.  Solutions  of 
the  salt  rapidly  absorb  oxygen  and  deposit  basic  ferric  sulphate. 

Ferro-us  bicarbonate,  FeC2O5,  (FeO  2  CO2),  occurs  in  mineral 
waters,  called  "  chalybeate  "  waters.  Such  waters,  on  exposure  to 
the  air,  absorb  oxygen  and  deposit  ferric  hydrate,  2  Fe2O3  3  H2O. 
A  brown  bulky  precipitate  of  hydrate,  having  the  composition 
Fe2H6O6,  is  obtained  when  ammonia  is  added  to  solutions  of  ferric 
salts.  Ferric  oxide  or  sesquioxide  of  iron,  "  iron  rust,"  is  Fe2O-, .  It 
combines  with  acids  to  form  ferric  salts.  Most  of  these  are  very 
vsoluble.  Ferric  chloride,  Fe2Cl6,  may  be  obtained  by  sublimation 
in  brown  scales,  which  very  rapidly  absorb  water  from  the  air  and 
deliquesce,  or  liquefy,  to  an  orange-red  solution.  Ferric  nitrate, 


82  GENERAL   OHEMI8TEY. 

Fea  t>  NOS,  12  aq.,  is  very  soluble.  In  conjunction  with  tannins  it 
forms  a  black  dye.  Ferric  oxide  may  take  the  place  of  alumina, 
A12OS,  in  the  formation  of  ferric  alum:  thus  K2Fes 4  SO4,  24  aq.,  is 
potash  ferric  alum.  Ferric  oxide  has  received  a  curious  applica- 
tion in  the  manufacture  of  caustic  soda  from  soda-ash,  sodium 
carbonate.  When  ferric  oxide  is  furnaced  at  a  low  red  heat  with 
soda-ash,  a  compound  of  the  iron  and  soda,  probably  sodium  ferrate, 
Na2FeO2,  is  formed,  from  which  hot  water  extracts  sodium  hydrate, 
NaHO,  leaving  ferric  oxide,  which  has  but  to  be  dried  to  be  again 
ready  for  use  in  the  same  operation. 

Ferrous  salts  are  very  readily  changed  into  the  corresponding 
ferric  salts  by  means  of  oxidizing  agents,  as  by  boiling  with  nitric 
acid,  or,  in  the  cold,  by  hypochlorites,  etc. ;  and,  conversely,  ferric 
salts  are  readily  changed  to  ferrous  salts  by  reducing  agents,  such 
as  nascent  hydrogen,  hydrogen  sulphide,  sulphurous  acid,  etc. 

MANGANESE. 

Symbol,  Mn.  —  Molecular  weight,  65.  —  Specific  gravity,  8.01. 

Manganese  is  a  grayish  white,  brittle  metal,  never  occurring 
native.  It  was  discovered  by  Gahn  in  1774.  The  metal  oxidizes 
rapidly  in  the  air,  and  decomposes  water  slowly  at  the  ordinary 
temperature.  It  is  prepared  from  manganous  carbonate,  MnCO8 , 
by  heating  to  whiteness  in  a  smith's  forge  with  charcoal.  The 
metal  alloys  readily  with  iron  to  render  the  latter  harder  and  more 
elastic.  Manganese  occurs  in  a  variety  of  combinations.  Its  most 
valuable  ore  is  pyrolusite,  MnO2. 

Manganese  forms  two  basic,  two  indifferent,  and  two  acid  oxides. 
Manganese  oxide,  MnO,  is  an?  olive-green  substance,  which  when 
ignited  in  the  air  absorbs  oxygen  and  is  changed  into  brown 
manganous-manganic  oxide.  Manganous  oxide  is  a  powerful  base. 
Most  of  its  salts  are  pink  or  rose  red. 

Manganic  oxide,  Mn2O3,  occurs  in  a  natural  form  as  mangahite. 
It  is  a  feeble  base.  It  may  be  substituted  for  alumina  and  ferric 
oxide  in  alums  and  other  compounds.  This  oxide  gives  a  violet 
color  to  glass,  and  the  color  of  the  amethyst  is  aiao  due  to  the  same 
substance. 

Manganous-ioanganic  oxide,  Mn3O4,  is  formed  by  the  ignition  of 
any  of  the-  other  oxides  of  manganese  with  free  contact  of  air.  It 
is  not  basic. 


COBALT. 


Manganese  dioxide  or  peroxide,  MnO2,  is  the  most  useful  ore  of 
manganese.  It  is  not  basic.  When  strongly  ignited  it  gives  off 
oxygen,  and  is  converted  into  Mn8O4.  When  heated  with  sulphuric 
acid  it  also  evolves  oxygen.  When,  heated  with  hydrochloric  acid 
chlorine  is  given  off,  arid  manganous  chloride  is  formed  according 
to  the  equation  — 

4  HC1  +  MnO2  =  C12  +  MnCl2  +  2  H20. 

Manganic  acid,  H2MnOs  (the  anhydride  being  MnO2),  is  green. 
The  manganates  are  very  unstable.  Their  solutions,  as  well  as 
those  of  the  permanganates,  form  powerful  disinfectants. 

Permanganic  acid,  H2Mn2O7  (anhydride,  Mn  Ofl),  is  scarcely 
known  except  in  combination.  Potassium  permanganate,  K2Mn2O7, 
is  a  dark  purple  salt,  crystallizing  in  needles.  It  yields  up  a  por- 
tion of  its  oxygen  very  readily  to  oxidizable  substances,  being  at 
the  same  time  reduced  to  MnO2  or  MnO.  Its  use  as  a  bleaching 
agent  has  been  proposed,  and  as  such  it  is  very  effective  under 
favorable  conditions,  but  the  expense  of  the  substance  and  of 
its  use  has  hitherto  prevented  its  extensive  employment  for  this 
purpose. 

Solutions  of  permanganates  form  very  efficient  deodorizers  and 
disinfectants.  The  oxides  of  manganese  and  many  of  its  salts  find 
extended  application  in  the  arts. 

COBALT. 

Symbol,  Co.. —Atomic  weight,  68.6.  — -  Specific  gravity,  8.95. 

Cobalt  is  a  reddish  white,  brittle  metal,  difficultly  fusible.  ]t  is 
magnetic  and  very  tenacious.  It  was  discovered  by  Brandt  in 
1783.  The  best  ore  of  cobalt  is  the  arsenide,  As2Co,  or  speisa- 
cobalt.  Cobalt  forms  two  oxides,  cobaltous  oxide,  CoO^  of  a 
greenish  color,  and  cobaltic  oxide,  Co2O8,  which  is  black.  The 
former  is  used  as  a  pigment,  "  Smalt "  is  a  glass  colored  blue  by 
oobaltous  silicate.  The  salts  of  cobalt  are  blue,  pink,  and  red. 
Unsized  paper  which  has  been  impregnated  with  a  solution  of  cobalt 
chloride  is  blue  in  dry  weather,  but  turns  pink  when  exposed  to  a 
moist  atmosphere.  Such  papers,  made  up  into  various  fanciful 
articles,  are  sold  in  France  as  a  sort  of  weather  indicator. 


84  GENERAL   CHEMISTRY. 

NICKEL. 

Symbol,  Ni.—  Atomic  weight,  58.8.  —  Specific  gravity,  8.8. 

Nickel  is  a  hard,  bluish  white,  difficultly  fusible  metal,  capable 
of  receiving,  a  high  polish.  It  is  tenacious  in  a- high  degree.  Nickel 
nearly  always  accompanies  cobalt  in  its  ores.  It  also  resembles 
the  latter  in  many  respects.  The  chief  ores  of  nickel  are  the 
arsenide  or  "  Kupfer-nickel,"  As2Ni2,  the  diarsenide,  As2Ni,  and  the 
arsenic-sulphide,  AsNiS.  The  metal  is  obtained  by  the  ignition  of 
nickel  oxalate  in  a  wind  furnace,  or  by  reducing  the  oxide  by  igni- 
tion with  carbon.  Nickel  is  magnetic  at  the  ordinary  temperature, 
but  loses  this  property  at  350°  C.  It  is  not  easily  acted  on  by 
acids,  with  the  exception  of  nitric  acid.  "  German  silver  "  is  an 
alloy  of  copper,  zinc,  and  nickel,  being  practically  CusZn3Ni2. 

Nickel  forms  one  basic  oxide,  nickel  oxide,  NiO,  and  an  indiffer- 
ent oxfde,  nickel  peroxide,  NiaO3 .  The  caustic  alkalis  precipitate 
nickel  hydroxide,  NiH^Og,  from  solutions  of  nickel  salts,  as  a  bulky, 
light  green  precipitate^  insoluble  in  potash  and  soda,  but  soluble  in 
ammonia  to  a  blue  solution.  The  latter  solution  has  the  property 
of  dissolving  silk,  while  it  does  not  dissolve  cellulose. 


CHROMIUM. 

Symbol,  Cr.  —Atomic  weight,  52.2.— Specific  gravity,  6.81. 

Chromium  is  a  steel-gray  metal,  more  intractable  than  platinum. 
It  was  discovered  by  Vauquelin  in  1797.  It  is  insoluble  even  hi 
aqua  regia.1  Never  native.  The  metal  may  be  obtained  by  strong 
ignition  of  the  oxide  with  charcoal  in  a  wind  furnace.  Chromium 
forms  two  basic  oxides,  chromous  oxide,  €rO,  and  chromic  oxide, 
Oi^Os.  The  latter  is  a  green,  earthy  substance,  often  employed  as 
a  pigment  and  to  give  a  green  color  to  porcelain  and  glass.  It- 
gives  to  the  emerald  and  to  serpentine  their  characteristic  colors. 
Chromic  oxide  may  replace  alumina  in  the  formation  of  alums. 

Chromium  also  forms  an  acid  oxide;  CrO3,  chromic  anhydride, 
which  forms  brilliant,  dark  red  deliquescent  prisms.  Chromic 
acid,  H2CrO4,  is  the  most  important  compound  of  chromium. 
With  potash  it  forms  neutral  chromafce,  K2CrO4,  yellow,  and  the 

1  This  is  only  true  of  the  crystallized  metal  obtained  by  Fr6my. 


TIN.  85 

bichromate  or  red  chromate,  K2Cr2O7 .  Chromic  yellow  or  canary 
yellow  is  neutral  lead  chromate,  PbCrO4.  It  is  formed  when  a 
solution  of  a  chromate  is  added  to  a  solution  of  acetate  of  lead. 
Orange  mineral  is  basic  lead  chromate,  PbCrO4,  PbO. 

The  compounds  of  chromium,  in  which  the  latter  takes  the  part 
of  base,  are  of  little  importance.  They  are  all  remarkable,  as  well 
as  the  chromates,  for  the  beautiful  colors  of  the  salts  themselves, 
and  also  of  their  solutions. 

URANIUM. 

Symbol,  Ur.  —Atomic  weight,  120.  — Specific  gravity,  18.4. 

Uranium  is  a  steel-gray,  slightly  malleable  metal,  never  found 
native.  It  is  not  oxidized  at  ordinary  temperatures,-  but  burns 
when  strongly  heated.  In  its  chemical  properties,  as  also  in  most 
of  its  compounds,  it  bears  a  close  analogy  to  iron  and  manganese. 
The  ores  of  uranium  are  of  rare  occurrence,  and  the  element  is  of 
little  practical  importance. 


THE   TIN  GROUP. 

Tin  (Stannum)  :  Symbol,  Sn.  —  Atomic  weight,  118. 
Titanium:  Symbol,  Ti.  —       "          "         60. 

Zirconium:          Symbol,  Zr. —       «•          "         89.5. 
Thorium.  Symbol,  Th.—       "          "       231.6. 


TIN. 

Symbol,  Sn.  — Atomic  weight,  118.  —  Specific  gravity,  7.292. 

Tin  is  a  lustrous,  white,  malleable  metal,  never  found  native. 
It  possesses  but  little  ductility.  It  has  a  slight  but  peculiar  odor. 
When  a  bar  of  tin  is  bent  it  emits  a  peculiar  crackling  sound, 
called  the  "cry"  of  tin.  Tin  melts  at  228°  C.  When  strongly 
heated  in  the  air  it  burns  iivtosstannic  oxMe,  SnO2.  At  ordinary 
temperatures  it  tarnishes  slowly.  Hydrochloric .  acid  dissolves  tin 
slowly,  forming  stannous  chloride,  SnCl2.  Boiling  sulphuric  acid 
dissolves  it  to  stannic  sulphate.  Nitric  acid  does  not  dissolve  tin, 
but  changes  it  into  insoluble  metastannic  acid,  H2Sn5On,  4aq. 
Tin  is  a  very  valuable  metal  for  many  purposes,  both  in  the  pure 
form  and  as  alloyed  with  other  metals.  Pewter  is  four  parts  tin 


86  GENERAL   CHEMISTRY. 

and  one  part  lead.  Common  solder  is  usually  equal  parts  tin  and 
lead.  Bronze  is  an  alloy  of  copper  and  tin.  "  Phosphor  bronze  " 
contains  a  little  phosphide  of  tin,  to  which  its  peculiar  properties 
are  due. 

Tin  forms  two  oxides :  stannous  oxide,  SnO,  a  black,  crystal- 
line substance  which  rapidly  absorbs  oxygen,  and  becomes  stannic 
oxide,  SnO2;  stannous  hydroxide,  SnH2O2,  is  white  and  gelati- 
nous, very  soluble  in  solutions  of  caustic  potash  and  soda.  It  is  a 
powerful  base. 

Stannic  oxide,  SnO2,  is  a  yellowish  white,  insoluble  substance. 
This  is  found  as  cassiterite  or  tinstone,  and  forms  the  chief  ore  of 
tin. 

Stannic  acid,  H^SnOg,  is  formed  as  a  white  gelatinous  precipitate, 
by  adding  ammonia  to  a  solution  of  stannic  chloride.  It  is  insolu- 
ble in  ammonia,  but  forms  compounds  with  the  alkali  and  alkali 
earth  metals,  called  stannates.  Stannate  of  soda  is  Na2SnO8i,  3  aq. 

Stannous  sulphide,  SnS,  is  a  bluish  gray  substance,  formed  by 
fusing  together  tin  and  sulphur.  The  same  substance  is  precipi- 
tated as  a  brown  rated  sulphide  by  passing  hydrogen  sulphide 
into  a  solution  of  stannous  chloride.  "Mosaic  gold"  is  stannic 
sulphide,  SnS2 .  The  soluble  salts  of  tin  are  largely  used  in  dyeing 
as  mordants. 

TITANIUM. 

Symbol,  Ti. — Atomic  weight,  50. —  Specific  gravity,  6.3. 

Titanium  is  a  rare  element,  never  native.  The  chief  ore  is 
titanio  anhydride,  TiO2,  occurring  as  "Rutile,"  "Brookite,"  and 
"  Anatase."  Titanium  forms  comparatively  few  compounds,  and  is 
of  little  interest,  It  was  discovered  by  Gregor  in  1791. 


ZIRCONIUM. 

Symbol,  Zr.  —  Atomic  weight,  89.5.  ~-  Specific  gravity,  4.15. 

Zirconium  is  a  black  amorphous  powder,  assuming  some  lustre 
under  the  burnisher.  It  resembles  silicon  and  titanium,  and  under 
certain  circumstances  antimony. 


TUNGSTEN  (WOLFRAM).  87 

THORIUM. 

Symbol,  Th.  —  Atomic  weight,  231. 5. —Specific  gravity,  7.7  to  7.9. 

Thorium  is  a  metal  discovered  by  Berzelius  in  1828.  The 
metal  dissolves  easily  in  nitric  acid,  and  slowly  in  hydrochloric* 
acid.  It  forms  one  oxide,  which  is  white  and  very  heavy.  Tho- 
rium is  of  no  importance  in  the  arts. 

MOLYBDENUM. 

Symbol,  Mo. —Atomic  weight,  90.  — Specific  gravity,  8.62. 

Molybdenum  is  a  white,  brittle  metal,  very  difficultly  fusible.  It 
takes  its  name  from  the  Greek  word  /j,o\v/3Scuvai  a  piece  of  lead, 
which  its  chief  ore,  molybdenite,  resembles. 

It  forms  two  basic  and  one  acid  oxides.  The  basic  oxides  are 
molybdous  oxide,  MoO,  black,  and  mplybiic  oxide,  MoO2,  dark 
brown.  In  solutions  of  salts  of  molybdic  oxide,  alkalis  precipitate 
molybdic  hydroxide.  The  latter  is  readily  soluble  in  acids  giving 
redriolored  solutions.  Nitric  acid  changes  molybdic  oxide  to  molyb- 
dic anhydride,  MoO8,  which  may  unite  with  water  to  form  molybdic 
acid,  not  known,  however,  in  the  free  state.  Neither  the  metal  nor 
its  salts  are  of  much  technical  importance.  Some  of  the  molybdates 
of  the  alkalis  are  useful  in  the  laboratory  for  the  detection  and 
separation  of  phosphoric  and  arsenic  acids  and  the  precipitation  of 
certain  alkaloids. 

TUNGSTEN   (Wolfram). 

Symbol,  W.  — Atomic  weight,  184.  —Specific  gravity,  17.6. 

Tungsten  is  an  iron-gray  metal,  nearly  infusible.  Its  most  com- 
mon ore  is  wolfram,  tungstate  of  iron  and  manganese.  It  is  a 
difficult  metal  to  obtain  in  the  free  state,  but  irtety  be  alloyed 
with  some  difficulty  with  other  metals  by  simultaneous  reduction 
of  the  oxides.  It  forms  a  variety  of  compounds  with  oxygen,  some 
of  them  exhibiting  acid,  and  others  basic  properties.  Sodium  tung- 
state possesses  the  property  of  rendering  cotton  fabric,  etc.,  unin- 
flammable. 


GENERAL   CHEMISTRY. 


THE  ANTIMONY  GROUP. 


Antimony  : 

Symbol, 

Sb.  —  Atomic  weight^  122.0. 

Arsenic  : 

Symbol, 

As.  — 

75.0. 

Bismuth  : 

Symbol, 

Bi.  — 

210.0. 

Vanadium  '. 

Symbol, 

Va.— 

51.3. 

Niobium: 

Symbol, 

Nb.— 

94.0. 

Tantalum  : 

Symbol, 

Ta.— 

182.0. 

AWTIMONY. 

Symbol,  Sb.  —  Atomic  weight,  122.  —  Specific  gravity,  6.75. 

Antimony  is  a  brilliant,  bluish  white  metal,  crystalline,  and  so 
brittle  that  it  may  be  powdered  in  a  mortar.  It  melts  at  450°  C., 
and  in  the  air  burns  brilliantly  with  the  formation  of  antimonou* 
oxide,  Sl^Oa  •  Strong  hydrochloric  acid  dissolves  the  metal  slowly, 
forming  antimonous  chloride,  SbCl3.  In  chlorine  gas  the  metal 
takes  fire,  and  burns  to  SbCl3 .  Nitric  acid  converts  it  into 
antimonic  acid,  HSbO3.  Antimony  alloys  readily  with  most  other 
metals.  Type  metal  consists  of  two  parts  lead,  one  part  tinr  and 
one  part  antimony,  the  latter  being  added  to  give  hardness  and 
stiffness  to  the  type,  and  also  to  cause  the  metal  to  expand  in  cool- 
ing, and  so  take  the  fine  lines  of  the  mold.  "Britannia  metal"  is 
nine  parts  tin  and  one  part  antimony.  Antimonous  hydride,  or 
stibine,  H3Sb,  is  formed  when  hydrogen  is  liberated  by  zinc  and 
acid  in  the  presence  of  any  compound  of  antimony.  It  is  a  color- 
less, fetid  gas,  which  burns  with  a  greenish  flame  to  water  and 
antimonous  oxide;  or,  when  the  supply  of  air  is  insufficient,  to  water 
and  antimony. 

Antimony  forms  with  chlorine  antimonous  chloride,  SbCls ;  anti- 
monous  oxychloride,  SbCIO  ;  and  antimonic  chloride,  SbCl5.  Anti- 
monous sulphide,  Sb2S3,  is  of  a  beautiful  orange  color.  Antimonic 
sulphide,  SbgSs,  is  also  orange  red. 

Antimonous  oxide,  SbsOs,  occurs  native  as  "  white  antimony  ore." 
It  is  a  gray  white  crystalline  powder,  becoming  yellow  on  heating-. 
It  js  soluble  in  hydrochloric  acid,  and  in  tartaric  acid  solution  to 
form  chloride  or  tartrate  of  antimony.  The  latter  is  the  "  tartar 
emetic  "  of  the  pharmacists.  When  heated  in  the  air  antimonous 
oxide  burns  to  antimonous  antimonate,  Sb2O4» 


VANADIUM. 


Antimonic  anhydride,  Sb2O5,  is  a  pale  yellow,  tasteless,  insoluble 
powder.     United  with  water  it  forms  antimonic  acid,  HSbO3. 


It  forms  antimonates  with  the  basic  oxides.  Metantimonic  acid 
is  H4Sb2O7.  Metantimonate  of  sodium  is  interesting  as  being  tire 
only  compound  of  sodium  with  an  inorganic  acid  which  is  insoluble 
in  water. 

Antimony  and  its  compounds  bear  a  close  analogy  to  the  corre- 
sponding forms  of  arsenic.  These  two  metals  appear  to  stand,  as  it 
were,  on  the  border  line  between  the  metals  and  the  iron-metallic 
elements.  Antimony,  however,  has  the  metallic  character  more 
distinctly  than  arsenic.  Both  have  the  property  of  rendering  other 
metals  with  which  they  are  alloyed  hard  and  brittle. 

Arsenic  has  been  previously  noticed  under  the  non-metallic 
elements. 

BISMUTH. 

Symbol,  Bi.  —Atomic  weight,  210.  —Specific  gravity,  9.79. 

Bismuth  is  a  beautiful  crystalline  metal,  of  a  reddish  white  hue. 
It  melts  at  264°  C.  When  strongly  heated  in  chlorine  gas  bismuth 
burns  with  a  bluish  flame,  forming  the  terchloride,  BiCl3.  Bismuth 
has  the  property  of  lowering  to  a  remarkable  degree  the  melting- 
point  of  alloys  of  which  it  forms  a  part.  Fusible  metal  is  an  alloy 
of  eight  parts  bismuth,  five  parts  lead,  and  three  parts  tin.  This 
alloy  melts  at  98°  C. 

Similar  alloys,  made  in  such  proportions  that  they  fuse  at  some 
particular  temperature,  are  used  as  safety  plugs  in  boilers  and  for 
certain  joints  in  automatic  sprinklers.  Except  in  such  allays 
metallic  bismuth  is  little  used.  It  forms  four  oxides.  Some  of  its 
salts  are  medicines  of  importance,  especially  the  nitrate,  which  is 
also  used  for  giving  a  colorless  iridescent  glaze  to  porcelain. 


VANADIUM. 

Symbol,  V.  —Atomic  weight,  51,3.  —  Specific  gravity,  5.5. 

Vanadium  is  a  very  rare  metal,  discovered  by  Sefstrom  in  1830, 
and  never  found  native.     In  its  combinations  with  oxygen  it  is 


90  GENERAL   CHEMISTRY. 

analogous  to  nitrogen,  forming  five  oxides, —  V2O,  V2O2,  V,O4, 
V8O4,  and  V2O5.  The  highest  of  these,  V2O5,  forms  with  water, 
vanadic  acid,  HVO3,  and  the  salts  of  this  acid  are  the  only  com- 
pounds which  have  received  any  industrial  application.  Vanadium 
in  solution  is  remarkable  for  its  affinity  for  cellulose,  this  substance 
being  able  to  abstract  vanadium  from  a  solution  containing  only 
one  part  of  the  metal  in  a  trillion. 

Blitz  has  patented  a  process  for  reducing  wood  to  pulp  by  .the 
use  of  a  solution  of  sodium  sulphide,  containing,  to  every  cord  of 
wood,  fifteen  grains  of  vanadate  of  ammonia  dissolved  in  hydro- 
chloric acid.  We  cannot  believe  that  the  efficiency  of  the  solu- 
tion is  in  any  way  increased  by  this  homoeopathic  addition. 

NIOBIUM. 

Symbol,  Nb.  —Atomic  weight,  94.  — Specific  gravity,  4.06. 

Niobium  is  a  rare  element,  never  native.  It  is  sometimes  called 
Columbium,  on  account  of  its  having  been  first  discovered  by  Hatch- 
ett  in  columbite  in  1801.  It  greatly  resembles  phosphorus  in  its 
combinations. 

TANTALUM. 

Symbol,  Ta.  —Atomic  weight,  182. 

A  rare  metal,  about  whose  properties  little  is  known.  Discov- 
ered by  Ekeberg  in  the  mineral  called  tantalite. 


THE  LEAD 


Symbol.     Atomic  weight. 

Specific  gravity.     Fusing-point. 

Lead: 

Pb. 

207.0 

11.38 

326°  C. 

Thallium: 

TL 

203.6 

11:86 

294°  C. 

Copper: 

Cu. 

63.4 

8.95 

1091°  C. 

Gallium: 

Ga. 

68.0 

6.90 

30.1°  C. 

Indium  : 

In. 

113.4 

7.40 

176°  C. 

(Plumbum) . 

Symbol,  Pb.  — Atomic  weight,  207.  T—  Specific  gravity,  11.38. 

Lead  is  a  bluish-colored  metal,  soft,  malleable,  and  ductile,  but 
little  tenacious.  It  tarnishes  slowly  in  moist  air.  It  is  acted 
upon  to  a  considerable  extent  by  soft  water  in  the  presence  of  air 


LEAD   (PLUMBUM).  91 

and  carbonic  acid,  also  by  water  containing  chlorides  and  nitrites. 
Hard  water  and  that  containing  sulphates  does  not  attack  lead. 
Hence  lead  poisoning  need  not  be  feared  from  the  use  of  water 
which  contains  sulphates.  Lead  oxidizes  rapidly  when  melted  in 
the  air,  forming  the  yellow  oxide,  PbO,  litharge.  On  further 
heating  litharge  takes  on  more  oxygen  and  becomes  red  lead  or 
minium,  Pb^,  sometimes  called  "orange  mineral."  At  a  still 
higher  temperature  red  lead  loses  oxygen,  and  is  changed  back  to 
litharge.  Two  other  oxides  of  lead  are  known;  the  suboxide, 
Pb2O,  which  is  black,  and  the  peroxide,  PbO2,  which  is  brown. 

Lead  is  never  found  native.  Its  chief  ores  are  galena,  lead 
sulphide,  which  usually  carries  more  or  less  silver  sulphide,  and 
the  peroxide  known  as  "heavy  lead  ore,"  or  puce  lead.  Lead 
expands  with  heat,  like  other  metals,  but  is  peculiar  in  that  it 
does  not  return  to  its  former  dimensions  on  cooling,  a  bar  or  sheet 
of  the  metal  growing  continually  larger  and  correspondingly  thinner 
with  each  successive  heating  and  cooling.  On  this  account  in 
a  boiler  lined  with  lead  the  lining  soon  becomes  too  large  for  the 
shell,  and  either  breaks  or  wrinkles  at  the  weakest  points  after  a 
certain  number  of  hedtings  and  coolings. 

Dilute  sulphuric  and  hydrochloric  acids  have  scarcely  any  action 
on  lead.  Chemically  pure  lead  is,  however,  attacked  to  a  greater 
extent  than  that  containing  traces  of  other  metals.  It  resists  the 
action  of  sulphurous  acid  perfectly,  and  consequently  is  of  great 
value  in  the  sulphite  process. 

Nitric  acid  dissolves  it  readily,  forming  nitrate  of  lead,  Pb(NO3)2. 
Strong  sulphuric  acid  scarcely  attacks  lead  at  moderate  tempera- 
tures, but  at  about  300°  C.  it  dissolves  it  so  rapidly  as  to  almost 
produce  explosion.  Sulphate  of  lead,  PbSO4,  is  a  white,  insoluble 
substance.  It  is  formed  when  sulphuric  acid  or  a  soluble  sulphate 
in  solution  is  added  to  the  solution  of  a  soluble  lead  compound. 
Hence  Glauber's  salts,  sulphate  of  soda,  or  "  Epsom  salts,"  sul- 
phate of  magnesia,  are  the  antidotes  for  lead  poisoning.  "  Sulphu- 
ric acid  lemonade,"  which  is  water  soured  by  sulphuric  acid  and 
flavored  with  lemon,  is  used  by  workmen  employed  in  white  lead 
works  as  a  preventive  of  lead  poisoning.  Sulphate  of  lead  is  fre- 
quently employed  as  an  adulterant  of  "  white  lead,"  which  }s  the 
basic  carbonate  of  lead,  PbH2O2,  2  PbCO3.  The  normal  carbon- 
ate is  PbCO8 . 

All  adulterants  of  white  lead  injure  its  qualities  as  a  paint. 


92  GENERAL   CHEMISTRY. 

Nitrate  of  lead  Pb  (NO3)2  is  a  white  crystalline  substance  soluble 
in  eight  parts  of  water.  Acetate  or  "  sugar  "  of  lead,  Pb  (C2HsO2)2, 
3  aq^is  soluble  in  twice  its  weight  of  water.  Chromate  of  lead, 
chrome  yellow,  PbCrO4,  is  formed  when  a  solution  of  bichromate 
of  potash  or  soda  is  added  in  excess  to  a  solution  of  'acetate  of 
lead  as  a  beautiful  yellow  precipitate  entirely  insoluble  in  water, 
By  boiling  the  yellow  chroinate  of  lead  with  lime  water,  a  portion 
.of  the  chromic  acid  combines  with  the  lime,  leaving  basic  lead 
vchromate,  PbgCrOs  (or  PbO,  PbCrO4),  which  is  an  orange  red, 
aknost  approaching  vermilion.  This  is  also  sometimes  called 
orange  mineral.  Flint  glass  is  a  silicate  of  lead  and  potash. 
**  Paste  "  for  imitation  gems  is  also  a  silicate  of  potash  and  lead, 
containing  more  lead  than  flint  glass. 

THALLIUM. 

Symbol,  Tl.  —Atomic  weight,  203.6.  —  Specific  gravity,  11.86. 

Thallium  is  a  soft,  malleable,  crystalline  metal,  between  lead 
and  silver  in  color.  It  was  discovered  by  the  aid  of  the  spectro- 
scope, in  1861,  by  Crooks.  Thallium  melts  at,  294°  C!.  It  tar- 
nishes in  moist  air.  Heated  in  oxygen  to  315°  G.,  it  "burns  with 
a  green  light.  It  greatly  resembles  lead  in  its  properties,  and  also 
in  its  compounds.  It  has  found  scarcely  any  useful  applications. 
Thallium  compounds  are  poisonous. 

COPPER  (Cuprum). 

Symbol,  Cn,  —  Atomic  weight,  63.4.-— Specific  .gravity,  8.95. 

Copper  is  a  metal  of  a  rich  reddish  color,  often  found -native, 
notably  near  Lake  Superior*  where  it  occurs  sometimes  in  masses 
.of  tons'  weight,  and  often  containing  native  silver.  Copper  is -one 
cif  the  most  useful  of  metals^  It  is  malleable,  ductile,  and  tena- 
cious to  .a  high  degree.  .Kext  to  silver  it  is  the  best  conductor 
of  heat  «nd  electricity.  It  corrodes  but  slowly,  and  only  super- 
ficially, in  moist  air.  Seawater,  however,  acts  upon  it  rapidly. 
Copper  melts  at  1091°  C.  Heated  to  redness  in  the  air  it  oxidizes 
rapidly,  forming  first  red  cuprous  oxide,  Cu2O^  and  then  cupric 
oxide,  CuO. 

Dilute  Uydrochloric  and  sulphuric  acids  attack  copper  scarcely 
at  all  in  the  cold.  Sulphurous  acid  (moist)  corrodes  it  rapidly . 


COPPER   (C1TPRUM}.  98 


Nitric  acid  attacks  it  immediately.  Boiled  with  strong  sulphuric 
acid,  copper  is  slowly  dissolved  as  copper  sulphate,  and  at  the 
same  time  sulphurous  acid  gas,  SO2,  is  given  off  according  to  the 
equation-  Cu  2  =  CuS()  gO  2 


This  reaction  furnishes  a  convenient  means  of  preparing  sulphurous 
anhydride,  SO2,  in  the  laboratory.  Chlorine  gas  combines  rapidly 
with  copper,  so  that  copper  foil  immersed  in  chlorine  takes  fire 
or  becomes  incandescent  from  the  heat  generated  by  the  rapid 
chemical  combination.  Copper  alloys  readily  with  many  of  the 
metals.  Brass  is  an  alloy  of  zinc  and  copper  ;  bell  metal  and  bronze, 
tin  and  copper,  etc. 

Copper  burns  with  a  green  flame  in  the  oxyhydrogen  flame. 
Its  salts  also  impart  a  green  color  to  flame. 

Copper  forms  two  basic  oxides  :  cuprous  oxide,  Cu2O,  red  ;  cupric 
oxide,  CuO,  black.  The  former  occurs  native  as  uruby  copper 
ore."  It  gives  a  ruby  color  to  glass.  The  cuprous  salts  are  color- 
less in  solution*  They  are  few  in  number,  and  of  little  importance 
in  the  present  connection. 

Cupric  oxide  or,  as  ordinarily  spoken  of,  copper  oxide,  CuO,  is 
black,  and  forms  with  acids  green  or  blue  salts.  Ordinary  "blue- 
stone,"  or  "blue  vitriol,"  is  cupric  sulphate,  CuSO*,  5  aq.  It  is 
soluble  in.  four  parts  of  water,  forming  a  blue  solution.  At  200°  C. 
all  the  water  of  crystallization,  or  combined  water,  is  driven  off,- 
and  the  salt  becomes  white. 

Cupric  chlJoridev  CuCl2  ,  2  aq.,  forms  green  deliquescent,  needles. 

Cupric  acetatev  Cu(C2H3O2)2,  H^O,  crystallizes  in  green  prisms. 
Verdigris  is  a  mixture  of  several  basic  cupric  acetates,  and  occurs 
in  both  a  green  and  blue  variety. 

Insoluble  salts  are  the  carbonate,  the  arseni'te  and  arsenate,  and 
the  aceto^arsenite,  the  latter  being  known  as  "  Paris  green." 

Cupric  oxide  is  soluble  in  oils  and  fats,  which  may  become 
poisonous  through  its  presence.  It,  however,  colors  them  green. 
It  also  gives  a  green  color  to  glass. 

Ammonia,  added  in  small  quantity  to  solutions  of  cupric  salts, 
precipitates  the  copper  as  cupric  hydrate,  CuH2O2,  of  a  light  green- 
ish blue  color.  Excess  of  ammonia  redissolyes  the  cupric  hydrate 
to  a  beautiful  deep  blue  solution.  Copper  is  precipitated  from  its 
solutions  by  iron,  zinc,  and  many  other  metals,  either  in  a  spongy 
form  or  as  a  coating  or  plating  on  the  surface  of  the  immersed 


GENERAL   CHEXLSTET. 


An  easy  test  for  the  presence  of  copper  in  a  solution  is 
to  immerse  in  it  a  piece  of  pnliArii  steel,  as  a  knife-blade,  when, 
if  even  a  email  amount  of  copper  is  ptcaent,  the  steel  will,  after  a 
short  time,  show  the  characteristic  color  of  copper. 

Copper  forms  the  best  r*m*ru  "al  for  conductors  and  pipes  of  a 
paper-mill,  as  the  alum  used  serves  to  keep  the  inside  of  the  pipes 
slime  is  leas  likely  to  find  a  lodgment  than 


Syvboi,  Ga.  —  Atoouc  ve^ki  68. — 

Gallium  is  a  hard,  white  metal,  resembling  aluminum  and  zinc. 
It  was  discovered  by  Lecoq  de  Boisbaudran  in  a  zinc  blende  in 
1975.  It  melts  at  80.1°  C.  Heated  to  redness,  it  only  oxidizes 
on  the  surface.  Gallium  oxide  may  be  substituted  for  alumina  in 
alums. 

The  metal  and  its  compounds  have  yet  found  no  practical  uses. 
It  is  of  infrequent  occurrence, 

nroiUM. 

Symbol,  In.  —  Atomic  weight,  113.4.  —  Specific  gravity,  7.42. 

Indium  is  a  rare  metal,  never  found  native.  It  was  discovered 
in  1863  in  a  German  zinc  ore.  It  is  a  white  metal,  malleable  and 
ductile.  It  melts  at  176°  C.  When  heated  to  redness  in  the  air 
it  burns  with  a  beautiful  violet-colored  flame,  forming  indium 
sesquioxide,  IntO,,  which  is  yellow.  Zinc  or  cadmium  (metallic) 
immersed  in  a  solution  of  indium  replaces  the  latter  and  precipitates 


SILVER  (ARGKNTUW).  95 


THE  SILVER   GROUP. 

SOMETIMES  CALLED  THE  NOBLE  METALS. 

Symbol.  Atomic -weight.    Specific  gravity.      Fnsmg-potat. 

Silver :             Ag.  108.0                10.63                  1»16°  C. 

Mercury:       Hg.  200.0               13.69                88.8°  O. 

Gold:              Au.  196.6                19.34                1037°  C. 

Platinum:      Pt  197.1                21.53                1460°  C. 

Palladium:    Pd.  106.5                11.80                1360°  C. 

Hhodium:      Rh.  104.3               12.10 

Huthenium :  Ru.  104.2               11.40 

Osmium:        Os.  199.0               22.48 

Indium:         IT.  198.0               21.15 


SILVER   (Argenttun). 

Symbol,  Ag. — Atomic  weight,  108.  — Specific  gravity,  10.53. 

Silver  is  frequently  found  native  both  in  the  crystalline  and 
massive  forms.  It  is  the  whitest  and  most  lustrous  of  all  the 
metals,  also  the  best  conductor  of  heat  and  electricity.  It  does  not 
tarnish  in  pure  air.  Its  oxide  is  reduced  to  metal  by  heat  alone. 
Silver  melts  at  916°.  When  melted  the  metal  will  absorb  twenty- 
two  times  its  bulk  of  oxygen  without  combining  with  it.  On  cool- 
ing the  absorbed  oxygen  is  discharged,  often  with  some  violent^ 
causing  "  sprouting  "  and  "  spitting  "  of  the  metal. 

Silver  has  a  great  affinity  for  sulphur,  being  rapidly  blackened 
and  converted  into  sulphide  of  silver  by  free  sulphur  or  soluble 
sulphides.  Sulphuric  and  hydrochloric  acids  scarcely  attack  silver 
at  all.  It  is,  however,  rapidly  attacked  by  nitric  acid,  and  dis- 
solved with  the  formation  of  nitrate  of  silver,  AgNO8.  Silver 
readily  alloys  with  other  metals.  Silver  coins  are  usually  alloys  of 
silver  and  copper  or  nickel. 

Silver  forms  three  oxides,  only  one  of  which  is  basic :  — 

Argentous  oxide,  Ag4O,  a  very  unstable  compound ; 

Argentic  oxide,  Ag2O,  which  is  a  brown  substance,  a  powerful 
base.  It  is  soluble  in  ammonia,  and  slightly  soluble  in  water.  At 
a  low  red  heat  it  is  decomposed  into  metal  silver  and  oxygen. 

The  peroxide,  Ag2O2,  is  formed  in  dark  gray  needles  by  the 
electrolysis  of  silver  nitrate. 

Argentic  sulphide,  Ag2S,  occurs  native  as  "  silver  glance."    The 


96  GENERAL   CHEMISTRY. 

same  substance  is  formed  when  hydrogen  sulphide  or  an  alkaline 
sulphide  is  added  to  a  solution  of  silver. 

Nitrate  of  silver,  AgNO3,  is  made  by  dissolving  silver  in  dilute 
nitric  acid,  evaporating  the  solution,  and  crystallizing.  It  thus 
forms  colorless  anhydrous  tabular  crystals.  The  crystals  melt  at 
219°  C.,  and  the  mass  may  then  be  cast  into  sticks,  which  form  the 
"  lunar  caustic  "  of  pharmacy.  Nitrate  of  silver  is  very  soluble  in 
water,  and  readily  so  in  alcohol.  Other  soluble  salts  of  silver  are 
the  sulphate,  Ag2SO4 ;  silver  alum,  AgjAl2  4  SO4,  24  aq.;  acetate, 
AgC2H3O2 ;  fluoride,  AgF ;  and  the  double  cyanide  of  silver  and 
potassium,  2  KCN,  AgCN,  H.2O.  The  latter  is  the  salt  commonly 
employed  in  silver-plating. 

All  the  soluble  silver  salts  are  irritant  poisons.  Their  antidote 
in  all  cases  is  common  salt,  NaCl. 

AH  salts  of  silver,  except  those  enumerated  above,  are  nearly  or 
quite  insoluble  in  water.  The  chloride,  bromide,  and  iodide  of 
silver  are  peculiarly  sensitive  to  light,  turning  nearly  black  on 
short  exposure  to  sunlight. 

The  art  of  photography  depends  upon  the  sensitiveness  of  the 
silver  salts  to  light.  The  "  plate  "  is  prepared  by  spreading  a  film 
of  albumen,  collodion,  or  gelatine,  carrying  the  bromide  and  iodide 
of  silver,  upon  glass.  When  the  plate  is  exposed  to  light,  as  in 
the  camera,  obscure  chemical  changes  take  place  which  affect  the 
subsequent  solubility  of  the  salts  in  the  fixing  or  reducing  bath. 
The  extent  of  the  change  is  proportional  to  the  amount  of  light 
falling  upon  different  portions  of  the  plate.  The  image  is  sub- 
sequently developed  by  contact  with  a  reducing  agent,  as,  for 
instance,  a  solution  of  ferrous  sulphate,  which  converts  those  por- 
tions of  the  silver  salts  which  have  been  affected  by  light  into 
metallic  silver.  The  image  is  fixed  or  rendered  permanent  by 
washing  out  the  undecomposed  silver  salts  by  a  solution  of  sodium 
thiosulphate  ("hyposulphite  of  soda").  If,  now,  paper,  similarly 
prepared  to  the  glass  plate,  is  exposed  to  light  under  this  "  nega- 
tive," the  silver  salts  are  blackened  where  the  light  comes  through 
the  negative,  and  the  "  positive  "  picture  so  obtained  may  be  fixed 
by  washing  in  a  bath  of  sodium  thiosulphate.  Paper  made  for 
photographic  purposes  should  be  free  from  acid,  antichlors,  and 
bleach,  since  these  affect  the  sensitive  silver  salts. 


MERCURY  (HYDRARGYRUM).  97 

MERCURY  (Hydrargyrum). 
Symbol,  Hg.  —  Atomic  weight,  200.  —  Specific  gravity,  13.59. 

Mercury  is  the  only  metal  known  which  is  fluid  at  the  ordinary 
temperature  of  the  air.  It  freezes  or  solidifies  at  —  38.8°  C.  Mer- 
cury is  rarely  found  native,  more  frequently  as  cinnabar,  mercuric 
sulphide,  HgS.  It  does  not  tarnish,  and  its  oxides  are  reduced  by 
heat -alone  ;  hence  it  is  called  a  "  noble  metal."  It  boils  at  357°  C., 
and  may  be  readily  distilled. 

Mercury  readily  alloys  with  other  metals.  Alloys  of  mercury 
are  called  amalgams.  It  amalgamates  with  gold  with  extreme 
facility,  dissolving  the  latter  almost  as  readily  as  water  dissolves 
sugar.  Advantage  is  taken  of  this  property  in  the  extraction  of 
gold  from  gold-bearing  quartz,  the  gold  being  dissolved  out  from 
the  powdered  rock  by  means  of  mercury,  and  the  resulting  amal- 
gam distilled  in  iron  retorts,  when  the  gold  remains  in  the  retort 
and  the  mercury  in  the  receiver  may  be  used  again.  The  amalgam 
of  tin  and  mercury  is  employed  for  "  silvering  "  mirrors.  At  300°  C. 
mercury  slowly  oxidizes,  forming  mercuric  oxide,  HgO.  Hydro- 
chloric acid  does  not  attack  mercury.  Nitric  acid  dissolves  it  in 
the  cold  to  mercurous  nitrate,  Hg2N2O6,  and,  when  heated,  to  mer- 
curic nitrate,  HgN2O6.  Heated  with  sulphuric  acid,  sulphurous 
acid  gas,  SO2,  is  given  off,  and  the  metal  is  dissolved  to  mercuric 
sulphate,  HgSO4. 

Mercury  forms  two  oxides,  both  basic.  Mercurous  oxide,  Hg2O, 
is  black  and  unstable.  It  forms  with  acids  mercurous  salts.  Mer- 
curic oxide,  HgO,  is  a  red  crystalline  powder.  Mercuric  oxide 
forms  with  acids  mercuric  salts. 

Calomel  is  mercurous  chloride,  Hg2Cl2.  Corrosive  sublimate 
is  mercuric  chloride,  HgCl2.  The  former  is  almost  entirely  insol- 
uble in  water  and  alcohol,  while  the  latter  is  very  readily  soluble 
in  both.  All  the  soluble  salts  of  mercury,  as  well  as  such  other 
of  its  compounds  as  may  become  in  any  degree  soluble  in  the 
system,  are  violent  acrid  poisons.  Their  antidote  is  raw  egg  albu- 
men, or  white  of  egg.  True  vermilion  is  an  artificial  mercuric 
sulphide,  Hg2S.  Mercuric  iodide,  HgI2,  is  also  of  a  vivid  scarlet 
color.  "  Turpeth  mineral "  is  yellow,  and  consists  of  basic  mer- 
curic sulphate,  HgSO4,  2  HgO. 

All  the  mercuric  salts  are  powerful  destroyers  of  organic  life, 
and  hence  are  frequently  of  the  highest  use  as  disinfectants.  One 


98  GENERAL   CHEMISTRY. 

part  of  .corrosive  sublimate  in  5000  of  water  has  been  found  to 
destroy  instantly  all  forms  of  bacteria. 


GOLD  (Aurum). 
Symbol,  Am  —  Atomic  weight,  190.6:  —  Specific  gravity,  19.34. 

Gold  is  always  found  native.  It  is  very  widely  distributed,  but 
occurs /only  in  comparatively  small  quantities.  It  is  a  bright  yel- 
low, lustrous  metal,  the  most  malleable  and  ductile  of  all  the 
metals.  Gold  leaf  is  often  only  TmjWff  of  ai*  inch  in  thickness. 
It  melts  at  1037°  C.  It  does  not  tarnish  in  the  air,  and  its  oxide 
is  reduced  by  heat  alone.  It  is  not  attacked  by  any  single  acid, 
but  is  readily  dissolved  as  auric  chloride,  AuCl3,  by  aqua  regia 
(hydrochloric  acid  three  parts,  to  nitric  acid  one  part).  It  is 
also  attacked  by  chlorine,  bromine,  and  iodine. 

Pure  gold  is  a  very  soft  metal,  and  hence  is  alloyed  with  a  per- 
centage of  copper,  which  renders  it  much  harder  and  better  able 
to  resist  wear.  As  a  conductor  of  heat  and  electricity,  gold  is  not 
so  good  as  silver  and  copper. 

The  compounds  of  gold  are  of  little  importance,  since  they  are 
only  used  for  a  few  special  purposes,  as,  e.  #.,  gilding  porcelain,  etc. 

PLATINUM. 

Symbol,  Pt.  —Atomic  weight,  197.1.  —Specific  gravity,  21.53. 

Platinum  is  a  white,  lustrous  metal,  resembling  tin  in  appear- 
ance, very  malleable  and  ductile.  It  was  discovered  in  1741.  It 
does  not  tarnish  in  the  air,  and  is  attacked  by  no  single  acid. 
Aqua  regia  dissolves  it  slowly  as  platinum  chloride.  It  is  also 
attacked  and  dissolved  slowly  by  chlorine,  bromine,  and  iodine  in 
presence  of  water.  Platinum  always  occurs  native  and  alloyed 
with  palladium,  osmium,  iridium,  rhodium,  and  ruthenium.  It  has 
been  found  in  greatest  quantity  in  the  Ural  Mountains,  but  even 
there  it  is  by  no  means  abundant.  It  has  been  found  also  in 
Brazil  and  Ceylon.  Platinum  melts  at  1460°  C.  Platinum  pos- 
sesses qualities  which  render  it  an  extremely  useful  metal,  but  the 
sparseness  of  its  distribution  in  nature,  together  with  the  difficulty 
of  working,  renders  its  cost  so  high  as  to  prohibit  its  use  in  all  but 
exceptional  instances. 


RUTHENIUM.  99 


Platinum  appears  to  be  the  only  metal  which  is  able  to  resist  the 
chemical  action  which  takes  place  at  the  positive  electrode  in  the 
processes  for  electric  "bleaching. 

The  stills  or  retorts  used  in  concentrating  sulphuric  acid  are  of 
platinum.  Vessels  made  of  this  metal  are  of  the  greatest  use  to 
Iho  chemical  analyst,  since  it  resists  the  action  of  nearly  all  chemi- 
cals as  well  as  great  heat. 


PALLADIUM. 

Symbol,  Pd.—- Atomic  weight,  106.6.  —  Specific  gravity,  11.8. 

Palladium  was  discovered  by  Wollaston  in  1803.  It  occasionally 
occurs  native,  but  usually  forms  one-half  to  one  per  cent,  of  the 
platinum  ores.  It  is  a  white,  lustrous  metal,  similar  to  platinum, 
but  much  harder.  It  melts  at  1360°  C.  It  is  dissolved  readily  by 
nitric  acid  and  aqua  regia.  Palladium  has  the  curious  property  of 
absorbing  hydrogen  equal  to  982  times  its  own  volume,  forming 
apparently  an  alloy  with  it.  Mercury  also,  under  certain  circum- 
stances, alloys  with  hydrogen  to  form  hydrogen  amalgam.  These 
reactions  seem  to  indicate  that  hydrogen  is  in  reality  a  metal. 
Palladium  occurs  only  in  very  small  quantities,  and  as  yet  no  con- 
siderable economic  use  has  been  found  for  it. 


RHODIUM. 

Symbol,  Rh.  — Atomic  weight,  104. 3. —Specific  gravity,  12.1. 

This  is  a  rare  metal,  of  no  industrial  importance,  found  alloyed 
with  platinum  in  its  ores,  usually  to  the  extent  of  about  one-half 
of  one  per  cent. 

RUTHENIUM. 

Symbol,  Ru.  —  Atomic  weight,  104.2.  —  Specific  gravity,  11.4. 

A  very  rare  metal  discovered  in  1845.  Never  native,  but  always 
alloyed  with  other  of  the  platinum  metals.  Of  no  industrial  im- 
portance. 


100  GENERAL   CHEMISTRY. 

OSMIUM. 

Symbol,  Os.  —  Atomic  weight,  199.  —  Specific  gravity,  22.48. 

A  rare  metal,  also  of  the  platinum  f amity,  discovered  in  1803. 
It  is  a  bluish  white,  very  infusible  metal.  It  takes  its  name  from 
the  Greek  word  007-0;,  meaning  smell,  on  account  of  the  pungent, 
irritating  odor  of  its  oxide,  OsO4,  whose  vapor  is  extremely  irritat- 
ing and  poisonous.  Osmium  is  the  heaviest  substance  known. 

IRIDIUM. 

Symbol,  Ir.-— Atomic  weight,  198.  —  Specific  gravity,  21.15. 

Iridium  was  discovered  in  1803.  It  sometimes  occurs  native, 
but  usually  as  an  alloy  with  osmium.  It  is  a  very  hard,  white, 
brittle  metal.  It  is  frequently  used  for  making  the  points  of  gold 
pens.  It  is  very  rare,  and  of  scarcely  any  importance  in  the  arts. 
It  takes  its  name  from  the  Latin  word  m*,-the  rainbow,  from  the 
rapid  changes  of  color  due  to  different  stages  of  oxidation  which 
occur  when  the  metal  is  heated. 


PART   II. 

THE   CHEMISTRY  OF  PAPER-MAKING. 


PAET   II. 
THE  CHEMISTRY  OF  PAPER-MAKING. 

CHAPTER  I. 

(CfiH1006) 


THE  physical  features  of  the  ordinary  forms  of  cellulose  are 
familiar  to  every  paper-  maker,  since  it  forms  the  basis  of  all  that 
he  produces.  It  is  essentially  vegetable  in  its  origin,  and  forms 
so  large  and  important  a  part  of  the  structure  of  all  plants  that 
it  has  been  said  that  in  the  vegetable  world  the  formation  of  cellu- 
lose may  be  considered  as  -.synonymous  with  growth.  Cellulose 
also  occurs  to  a  limited  extent  in  the,  animal  kingdom,  and  has 
been  found  in  the  brain,  in  diseased  human  spleen,  the  skin  of 
silkworms  and  of  serpents,  and  in  the  mantles  of  certain  molluscs. 

Cotton-  wool,  filter  paper,  and,  in  general,  any  vegetable  fibre 
which  has  undergone  the  usual  chemical  processes  of  paper-making 
consist  mainly  of  cellulose,  with  which  are  associated  various 
other  substances  in  greater  or  less  amount.  Pure  cellulose  is 
most  readily  obtained  by  treating  cotton-wool  or  white  filter  paper 
with  a  boiling  one  per  cent,  solution  of  caustic  soda,  then  with 
cold  dilute  hydrochloric  acid,  and  after  that  with  ammonia.  The 
fibre  should  be  carefully  washed  with  water  after  treatment  \vith 
each  of  these  reagents,  and  finally  exhausted  with  alcohol  and 
ether.  Thus  obtained,  cellulose  is  a  white,  translucent  body,  of 
Sp.  Gr.  about  1.45,  and  which  preserves  the  form  and  general 
character  of  the  fibres  from  which  it  was  prepared.  It  resists  the 
action  of  chemical  reagents  to  a  remarkable  degree,  as  is  shown 
by  its  wide  use  in  the  laboratory  in  the  form  of  filter  paper. 
Cellulose  has,  however,  a  powerful  attraction  for  certain  salts  in 
solution,  and  water  containing  them  may  be  so  filtered  through 

103 


104",  i  ;<  1  ;  !  :<?^#  [qdEMipTRY  OF  PAPER-MAKING. 


a  mass  of  cellulose  as  to  have  the  dissolved  salts  completely 
removed.  This  attractive  power  is  so  strong  in  the  case  of  vana- 
dium compounds  that  cellulose  will  separate  them  from  solutions 
containing  only  one  part  of  the  salt  in  a  trillion. 

Solutions  of  iron  and  alumina  salts  in  contact  with  a  quantity 
of  pulp  may  have  a  considerable  portion  of  the  base  fixed  upon 
the  fibre.  Where  iron  is  present,  the  color  may  thus  be  seriously 
affected.  The  process  of  mordanting  cotton  goods  depends  upon 
this  affinity  of  cellulose  for  metallic  bases. 

The  formula  for  cellulose,  C6H10OM  does  not  indicate  the  pres- 
ence of  any  mineral  constituents,  but  even  its  most  carefully  puri- 
fied forms  leave  an  appreciable  amount  of  ash.  In  cotton  this  is 
usually  from  0.1  to  0.2  per  cent.,  though  Herzberg  gives  a  figure 
as  high  as  0.41  per  cent.,  and  bleached  filter  paper  which  has  been 
washed  with  both  hydrochloric  and  hydrofluoric  acids  leaves  suffi- 
cient ash  to  render  a  correction  for  its  presence  necessary  in  very 
careful  chemical  work. 

The  various  reactions  of  cellulose  prove  it  to  be  closely  related 
to  the  sugars,  starch,  dextrin,  glucose,  and  other  members  of  that 
group  of  bodies  which,  including  cellulose,  are  termed  carbohy- 
drates. The  formula  of  cellulose  is  the  same  as  that  of  starch, 
and,  like  starch,  cellulose  can  be  readily  converted  into  dextrin 
and  glucose.  (See,  also,  Cellulosic  fermentation,  p.  116.) 

The  only  known  liquid  in  which  cellulose  dissolves  without 
undergoing  chemical  change  is  Schweitzer's  reagent,  as  it  is  called, 
though  it  is  stated  (Life  of  John  Mercer,  London,  1886)  that 
its  action  was  first  studied  by  Mercer.  This  reagent  may  be  pre- 
pared in  various  ways.  Our  own  experience  has  led  us  to  prefer 
the  following  method  :  cupric  hydrate  is  precipitated  by  adding  a 
solution  of  caustic  soda  to  a  cold  solution  of  copper  sulphate  until 
nearly  all  the  copper  is  precipitated.  The  hydrate  is  then  carefully 
washed,  and  may  be  preserved  under  water  in  a  glass-stoppered 
bottle.  As  the  reagent  is  needed  for  use,  it  is  made  by  dissolving 
the  hydrate  in  ammonia  of  Sp.  Gr.  0.900,  until  a  saturated  solution 
is  obtained.  When  treated  with  Schweitzer's  reagent,  cellulose  at 
first  swells  up  and  becomes  gelatinous,  but  finally  dissolves  com- 
pletely to  a  thick  syrupy  solution.  Erdmann  and  other  chemists 
have  contended  that  no  true  solution  is  formed,  but  recent  experi- 
ments by  Cramer  on  the  osmotic  properties  of  the  solution  prove 
that  the  cellulose  is  really  dissolved.  From  this  solution  it  may 


CELLULOSE.  105 


be  precipitated  in  gelatinous  flocks  by  the  addition  of  acids,  many 
salts,  and,  it  is  generally  said,  by  simply  diluting  it  largely  with 
water  and  allowing  the  solution  to  stand  in  a  closed  vessel  for  eight 
to  ten  da}Ts.  We  think  it  doubtful  if  complete  precipitation  is  ob- 
tained in  this  way,  and  we  have  allowed  such  dilute  solutions, 
containing  less  than  0.25  gram  of  cellulose  per  litre,  to  stand  in 
glass-stoppered  jars  for  more  than  a  month  without  causing  any 
precipitation.  The  precipitate,  as  usually  formed,  contains,  in 
addition  to  cellulose,  considerable  copper  hydrate,  which  gives  it 
a  blue  color,  and  which  may  be  removed  by  washing  with  water, 
dilute  acid,  and  then  with  water  again.  When  a  solution  of  lead 
acetate  is  used  to  precipitate  the  cellulose,  the  precipitate  contains 
both  cellulose  and  lead  oxide  in  varying  proportions ;  while  by 
digesting  the  same  solution  with  finely  divided  lead  oxide  a  defi- 
nite compound  of  cellulose  and  lead  oxide  (CfiH,0Ofi,  PbO)  is 
obtained.  Metallic  zinc,  added  to  the  solution  of  cellulose  in 
Schweitzer's  reagent,  throws  down  the  copper,  which  is  replaced 
by  zinc,  forming  a  colorless  solution  similar  in  its  properties  to 
the  original  one. 

A  practical  application  of  the  action  of  Schweitzer's  reagent 
upon  cellulose  has  been  made  on  the  large  scale  in  the  manufac- 
ture of  the  so-called  Willesden  papers  and  products.  The  reagent 
is  prepared  in  quantity  in  a  series  of  towel's,  loosely  packed  with 
copper  scrap,  over  which  strong  ammonia  is  allowed  to  trickle, 
while  air  is  drawn  up  through  the  towers.  When  a  web  of  paper 
is  passed  through  this  solution,  the  fibres  become  superficially 
softened,  and  may  be  pressed  into  a  continuous  mass,  or  several 
sheets  may  be  pressed  together.  No  attempt  is  made  to  wash  out 
the  solution,  which  dries  to  a  green  varnish,  coating  the  fibres,  and 
rendering  them  waterproof  and  very  durable.  Canvas  and  rope 
cordage  are  similarly  treated. 

A  solution  of  iodine,  prepared  by  dissolving  one  gram  of  iodine 
and  five  grams  of  iodide  of  potash  in  100  c.c.  of  water,  stains  cellu- 
lose blue  under  certain  conditions,  and  is  used  for  its  recognition 
under  the  microscope.  If  Iceland  moss  or  some  of  the  lichens  and 
algee  containing  cellulose  in  its  less  compact  forms  are  merely 
boiled  with  water,  the  cellulose  is  disintegrated,  and  the  blue  color 
is  obtained  on  adding  the  above  solution  of  iodine.  With  a  fresh 
solution,  cellulose  in  its  denser  forms,  as  in  cotton  and  other  puri- 
fied fibres,  merely  develops  a  yellow  color,  which  may  shade  into 


106  THE  CHEMISTRY  OF  PAPER-MAKING. 

brown;  but  if  the  fibres  are  first  treated  with  sulphuric  or  phos- 
phoric acid,  or  zinc  chloride,  they  are  then  stained  blue  with 
iodine.  It  would  seem,  therefore,  that  although  this  blue  colora- 
tion is  generally  spoken  of  as  characteristic  of  cellulose,  it  really 
depends  not  upon  cellulose,  but  upon  other  bodies,  whose  presence 
is  the  result  of  the  treatment  to  which  the  cellulose  has  been  sub- 
jected. Schultze's  solution  of  iodine  gives  a  blue  with  cellulose 
at  once,  and  may  be  prepared  by  dissolving  zinc  in  hydrochloric 
acid  so  long  as  there  is  any  action,  evaporating  the-  resulting  solu- 
tion of  zinc  chloride  to  a  syrup,  saturating  with  potassium  iodide, 
and  then  adding  enough  iodine  to  color  the  whole  brown.  It  may 
be  used  of  various  degrees  of  strength,  but  it  is  to  be  observed 
that  the  zinc  chloride  would  exert  a  powerful  action  upon  the 
cellulose,  so  that  in  this  case  also  the  blue  coloration  is  probably 
due  to  modifications  of  the  cellulose  rather  than  to  that  substance 
itself  and  iodine. 

Concentrated  sulphuric  acid,  Sp.  Gr.  1.60,  dissolves  pure  and 
thoroughly  dry  cellulose,  a  syrupy  and  almost  colorless  solution 
being  obtained,  which,  on  dilution  with  water  and  boiling,  is  con- 
verted into  dextrin  and  glucose.  If  the  boiling  is  continued  for  a 
long  time,  about  five  hours,  only  glucose,  or  similar  reducing 
sugars,  is  obtained.  As  the  glucose  can  be  readily  fermented, 
with  consequent  production  of  alcohol,  it  is  thus  possible  to  make 
both  glucose  and  alcohol  from  such  materials  as  sawdust  and  rags. 
Starch,  under  the  same  conditions,  acts  similarly  and  gives  the 
same  products.  With  more  concentrated  acid,  especially  if  it  be 
hot  or  if  the  cellulose  is  damp,  there  is  a  breaking  down  of  the 
cellulose  molecule,  and,  at  the  same  time,  more  or  less  decompo- 
sition of  the  acid.  Gases  are  evolved,  in  which  carbonic  and 
sulphurous  acids  may  be  recognized,  and  the  liquid  becomes  black 
from  the  separation  of  carbonaceous  matters.  These  are  precipi- 
tated on  pouring  the  acid  into  a  considerable  volume  of  water, 
and  may  be  easily  removed  by  filtration,  leaving  a  golden  colored 
liquid,  whose  color  darkens  when  the  acid  is  neutralized  with 
ammonia.  When  treated  with  acid  of  the  strength  previously 
given,  Sp.  Gr.  1.60,  or  even  with  somewhat  weaker  acid,  the 
cellulose  first  becomes  gelatinous  and  more  transparent.  If  the 
mixture  is  poured  into  water  before  the  solution  is  complete, 
white  flocks  resembling  hydrate  of  alumina  are  obtained,  which 
dry  to  a  tiorny  mass.  The  substance  composing  them  differs  little 


CELLULOSE.  107 


from  cellulose  in  composition,  and  is  termed  amyloid,  from  its 
resemblance  to  starch.  Its  composition  is  given  as  C^H^Ou.  It 
is  difficult  to  determine  just  when  the  cellulose  is  entirely  dis- 
solved, owing  to  its  transparency,  and  it  is  usually  stated  that  pre- 
cipitation of  amyloid  occurs  at  once  on  diluting  the  clear  solution. 
We  find  in  our  own  experiments,  using  various  strengths  of  acid, 
that  when  a  clear  solution  is  obtained  there  is  no  precipitation  of 
amyloid  upon  dilution  until  a  considerable  time  lias  expired,  when 
at  best  only  a  small  proportion  of  the  cellulose  is  recovered  in  that 
form.  The  loss  is  probably  due  to  the  formation  of  dextrin. 
Amyloid  forms  the  outer  coating  of  the  parchment  paper  which 
is  largely  used  in  dialyzing  apparatus  and  for  many  of  the  purposes 
to  which  animal  parchment  was  applied. 

Parchment  paper  is  prepared  by  dipping  unsized  paper  for  a  few 
seconds  into  sulphuric  acid  diluted  with  one-quarter  to  one-half  or 
more  its  bulk  of  water,  to  which  glycerine  is  sometimes  added. 
After  removing  the  paper  it  is  washed  with  water,  then  with  dilute 
ammonia  or  other  alkali,  and  finally  with  pure  water  again.  On 
the  large  scale  the  paper  is  treated  in  the  web  in  a  continuous  way, 
passing  into  the  acid,  as  into  a  vat  for  glue  sizing,  then  between 
rollers,  or  "  doctors,"  to  remove  the  excess  of  acid,  and  from  there 
into  the  dilute  ammonia  and  water.  Thus  treated,  the  paper  ac- 
quires a  remarkable  toughness  and  many  of  the  properties  of 
animal  parchment.  It  undergoes  a  considerable  linear  shrinkage 
during  the  treatment  (20  per  cent.),  and  suffers  some  loss  of 
weight  (Cross  and  Bevan).  The  action  of  a  concentrated  solution 
of  zinc  chloride,  about  65°  B6.  upon  cellulose  is  similar  to  that  of 
sulphuric  acid.  The  so-called  vulcanized  fibre  is  formed  of  sheets 
of  paper  which  have  been  treated  with  zinc  chloride,  then  pressed 
together,  and  washed  for  a  long  time  in  running  water  to  remove 
the  chemical. 

The  formation  of  parchment  paper  by  means  of  sulphuric  acid 
was  first  noticed  by  Poumardde  and  Figuier  in  1847,  from  whom 
it  received  the  name  Papyrin.  No  practical  application  of  their 
discovery  was  made  until  it  was  extended  and  patented  by  Gaines 
in  1857. 

The  process  has  quite  recently  received  an  ingenious  application, 
which  would  seem  to  make  any  alteration  in  the  denomination  of 
a  bank  note  or  other  paper  money  impossible.  The  denomina- 
tion is  printed  in  large  numbers  in  the  centre  of  the  bill,  the 


108  THE  CHEMISTRY  OF  PAPER-MAKING. 


numbers  being  preceded  and  followed  by  a  star  or  other  device, 
thus  — 

-4.1OOO4- 

Strong  sulphuric  acid  or  a  solution  of  chloride  of  zinc  is  used  in 
place  of  ink,  and  transforms  the  paper,  which  is  generally  tinted, 
into  transparent  vegetable  parchment  at  the  points  where  it  is 
deposited,  so  that  after  washing  and  drying  the  numbers  seem 
to  be  formed  by  a  tough  transparent  membrane  inserted  in  a 
colored  sheet.  The  effect  is  highly  artistic,  and  as  the  fibrous 
structure  of  the  paper  is  destroyed  at  the  points  where  the  chemi- 
cals were  deposited,  it  is  practically  impossible  to  alter  the  char- 
acters. 

When  cellulose  is  heated  in  a  sealed  tube  to  180°,  with  six  to 
eight  times  its  weight  of  acetic  anhydride,  it  dissolves  to  a  thick 
syrup.  On  pouring  this  into  water  white  flocks  of  triaceto- 
cellulose  are  precipitated,  which  have  the  composition  represented 
bv  the  formula  — 

C0H7(C2H30)305. 

The  compound  dissolves  in  strong  acetic  acid,  but  is  insoluble  in 
water,  alcohol,  and  ether.  Alkalis  easily  remove  the  acid  with 
recovery  of  the  cellulose.  This  reaction  is  similar  to  the  one  tak- 
ing place  when  oils  are  treated  with  alkali,  when  glycerine  is  set 
free,  and  soap  formed,  and  it  therefore  indicates  that  cellulose,  like 
glycerine,  may  be  considered  a  triatomic  alcohol.  This  view  is 
confirmed  by  the  fact  that  it  has  been  found  impossible  to  prepare 
compounds  containing  more  acetic  anhydride  than  the  above,  no 
matter  how  great  an  excess  of  the  anhydride  is  used  or  how  long 
the  heating  is  continued.  It  is  to  be  noted  also,  in  this  connection, 
that  by  the  action  of  nitric  acid  upon  cellulose  nitro-substitution 
products  are  formed  similar  in  many  of  their  properties  to  the 
nitroglycerines. 

The  action  of  nitric  acid  upon  cellulose  was  first  studied  by 
Pelouze,  who  observed  in  1838  that  it  resulted  in  the  conversion 
of  the  cellulose  into  an  explosive  substance.  Schonbein,  in  1846, 
announced  the  discovery  of  an  explosive  cotton,  but  kept  its 
method  of  preparation  secret.  It  was  independently  discovered 
soon  after  by  Bottger  and  Otto,  by  the  latter  of  whom  the  method 
was  published.  Several  disastrous  explosions  of  large  quantities 
of  the  material  as  at  first  made  caused  it  to  be  considered  utterly 


CELLULOSE.  109 


unfit  for  use,  until  von  Lenk  and  Abel  pointed  out  the  precautions 
necessary  to  secure  the  production  of  a  material  of  constant  com- 
position, and  which  remained  perfectly  stable  under  all  ordinary 
conditions.  Knop  had  previously  shown  that  a  mixture  of  nitric 
and  sulphuric  acids  gave  better  results  than  nitric  acid  alone,  and 
the  explosive  called  guncotton  is  now  prepared  as  follows  :  Loosely 
spun  yarn  or  cotton  wool  is  first  purified  by  boiling  in  a  dilute 
solution  of  carbonate  of  potash  to  remove  resinous,  gummy,  and 
waxy  matters  or  oil.  It  is  then  carefully  washed  with  water  and 
dried,  after  which  it  is  placed  in  a  mixture  of  one  part  of  nitric 
acid,  Sp.  Gr.  1.5,  and  three  parts  sulphuric  acid,  Sp.  Gr.  1.85,  and 
allowed  to  remain  twenty-four  hours.  Great  pains  are  taken  to 
keep  the  mixture  cool.  The  nitrated  cotton,  after  washing,  is 
removed  to  a  beating-engine,  where  it  is  washed  again  and  reduced 
to  pulp.  It  is  then  ready  to  be  pressed  into  hexagonal  blocks  or 
into  cylinders. 

The  composition  of  guncotton  was  determined  by  Crum,  who 
gave  it  the  formula  — 

CMH14(NOO«04, 

or  that  of  a  hex-nitrate  of  cellulose.  Guncotton  is  also  called 
Pyroxylin,  though  this  term  is  usually  extended  to  comprise  the 
other  nitrates  of  cellulose  as  well.  Its  general  appearance  is  the 
same  as  that  of  the  cotton  from  which  it  was  prepared,  but  it  is 
harsher  to  the  touch,  and  its  fibres,  viewed  under  the  microscope 
by  polarized  light,  do  not  show  the  brightness  and  play  of  color 
exhibited  by  ordinary  cotton.  It  becomes  strongly  electrical  on 
being  rubbed,  crackling  and  emitting  sparks,  and  is  phosphorescent 
in  the  dark  (Gaiffe).  It  is  slowly  soluble  in  acetone,  but  insoluble 
in  water,  methyl  alcohol,  glacial  acetic  acid,  Schweitzer's  reagent, 
alcohol,  or  ether,  or  in  mixtures  of  the  last  two  liquids.  Weak 
acids  and  alkalis  do  not  affect  it.  Strong  sulphuric  acid  dissolves 
it  slowly,  and  upon  heating  the  solution  carbonic  acid  and  nitric 
oxide  are  given  off,  though  there  is  no  blackening.  It  dissolves 
rapidly  in  strong  potash  lye  when  heated  to  70°,  with  formation  of 
ammonia,  nitrous  acid,  oxalic  acid,  and  other  bodies  of  acid  char- 
acter. The  alkaline  solution  precipitates  silver  from  an  ammonia- 
cal  solution  of  the  metal,  and  the  reaction  has  been  utilized  in  a 
process  for  silvering  mirrors.  Alkaline  solutions  of  moderate 
strength  remove  more  or  less  nitric  acid  from  guncotton  on  warm- 
ing, the  proportion  of  acid  removed  varying  with  the  strength  of 


110  TUE  CHEMISTRY  OF  PAPER-MAKING. 

the  solution  (Eder).  A  solution  of  potassium  sulphydrate  in 
dilute  alcohol  converts  the  nitrate  into  the  original  cotton,  potas- 
sium nitrate  and  some  ammonia  being  formed.  Ferrous  sulphate 
and  ferrous  acetate  or  a  solution  of  stannous  oxide  in  caustic  soda 
have  the  same  effect.  In  contact  with  sulphuric  acid  and  mercury, 
guncotton  gives  up  its  nitrogen  as  nitric  oxide.  These  reactions, 
like  that  with  acetic  anhydride,  indicate  that  cellulose  is  analogous, 
in  many  of  its  chemical  relations,  to  the  alcohols. 

Concentrated  sulphuric  acid  displaces  the  nitric  acid  in  gun- 
cotton  even  in  the  cold.  A  method  of  estimating  the  nitrogen  in 
pyroxylins  is  based  upon  the  fact  that  when  they  are  boiled  with 
ferrous  sulphate  and  hydrochloric  acid  the  nitrogen  is  set  free  as 
nitric  oxide  (Eder). 

Besides  guncotton,  which  contains  six  NO3,  there  have  been  pre- 
pared several  other  lower  nitrates  of,  cellulose,  containing  succes- 
sively five,  four,  three,  and  two  NO3.  They  differ  from  guncotton 
mainly  in  being  less  explosive,  and  in  the  fact  that  they  are 
soluble  in  a  mixture  of  alcohol  and  ether.  The  penta-nitrate, 
C12H15O5(NO3)3,  is  best  prepared,  according  to  Eder,  by  dissolving 
guncotton  in  -hot  nitric  acid,  about  90°  C.,  then  cooling  to  0°,  when 
it  is  precipitated  as  the  penta-nitrate  on  addition  of  sulphuric  acid. 
The  precipitate  is  washed  with  a  large  amount  of  water,  and  fur- 
ther purified  by  being  dissolved  in  a  mixture  of  alcohol  and  ether, 
from  which  the  pure  nitrate  is  thrown  down  on  addition  of  water. 
By  the  action  of  strong  solutions  of  potash  upon  the  penta-nitrate 
a  portion  of  the  acid  is  removed,  leaving  di-nitrate  of  cellulose. 

The  extent  to  which  the  nitration  of  the  cellulose  is  carried 
when  in  contact  with  the  mixed  acids  depends  upon  the  strength 
of  the  acids  employed  and  upon  the  time  for  which  it  is  exposed  to 
their  influence.  Thus,  by  shortening  the  time  of  immersion  to  a 
few  minutes,  or  by  the  use  of  weaker  acids,  a  mixture  of  the  tetra- 
nitrate,  CjallieOeCNOa)^  and  tri-nitrate,  C12Hi7O7(NO3)3,  is  obtained. 
These  are  readily  soluble  in  a  mixture  of  alcohol  and  ether,  in 
acetic  ether,  and  in  methyl  alcohol.  The  solution  in  ether-alcohol 
mixture  is  called  collodion,  and  the  tetra-  and  tri-nitrates  are 
termed  collodion  pyroxylins. 

The  di-nitrate,  C12H18O8(NO3)2,  is  the  result  of  the  action  of  a 
hot  dilute  mixture  of  nitric  and  sulphuric  acids  upon  cellulose. 
It  dissolves  in  the  solvents  mentioned  in  the  preceding  paragraph. 
All  of  the  higher  nitrates  are  finally  reduced  to  this  body  when 


CELLULOSE.  Ill 


treated  with  alkaline  solutions ;  but  if  the  action  is  carried  too  far, 
there  is  a  farther  decomposition  with  production  of  a  brown 
gummy  mass.  The  mono-nitrate  has  not  been  formed. 

Celluloid  and  zylonite  are  prepared  by  treating  the  lower 
nitrates,  collodion  pyroxylins,  with  camphor,  either  melted  or  AS 
spirits  of  camphor.  This  reduces  the  pyroxylin  when  hot  to  a 
plastic  condition,  in  which  it  can  be  readily  worked  and  moulded 
into  a  great  variety  of  articles,  and  which  permits  the  incorpora- 
tion of  coloring  matters  and  other  substances. 

Celluloid  in  the  mass  burns  about  as  readily  as  paper,  and  with 
a  smoky  flame.  It  cannot  be  exploded  by  any  ordinary  means. 
The  camphor  present  may  be  removed  by  ether.  Thin,  trans- 
parent plates  and  rolls  of  celluloid  are  now  much  used  in  photog- 
raphy, as  their  flexibility  and  lightness  give  them  great  advantage 
over  glass.  In  this  form  celluloid  flashes  up  quickly  and  burns 
without  smoke. 

Collodion  —  the  solution  of  pyroxylin  in  ether-alcohol  mixture 
—  rapidly  dries  on  exposure  to  the  air,  and  forms  a  tough,  lustrous 
varnish.  It  is  largely  used  in  surgery  as  a  covering  for  wounds, 
in  photography  as  a  vehicle  for  the  silver  salts,  and  in  the  match 
manufacture  for  rendering  the  tips  of  matches  waterproof.  Pure 
sulphite  fibre  or  unsized  paper  made  therefrom  is  sometimes  used 
instead  of  cotton  in  the  preparation  of  both  celluloid  and  col- 
lodion. 

The  nitrates  of  cellulose  and  their  reactions  have  received  a  new 
interest  for  the  paper-maker  through  their  recent  application  in  the 
process  of  manufacturing  artificial  silk.  This  product,  which  re- 
sembles silk  only  in  its  physical  properties,  was  first 
shown  at  the  Paris  Exposition  of  1889,  where  it  at- 
tracted much  attention.  It  is  prepared  by  the  follow- 
ing process  of  M.  de  Chardonnet :  — 

Cotton  or  pure  chemical  fibre  is  nitrated  and  dis- 
solved in  a  mixture  of  thirty-eight  parts  ether  to  forty- 
two  parts  alcohol  to  form  collodion.  This  is  placed 
in  a  copper  vessel,  and  forced  by  air  pressure  through 
capillary  glass  tubes  into  water.  In  Fig.  2,  A  shows 
the  glass  tube  through  which  the  collodion  passes. 
B  is  a  second  tube  surrounding  the  first,  and  supplied 
with  water  through  the  inlet  C.  The  collodion  solidifies  upon 
contact  with  the  water,  forming  a  smooth  thread,  which  is  carried 


112  THE  CHEMISTRY  OF  PAPER-MAKING. 


forward  by  suitable  mechanical  arrangements  through  a  drying 
chamber  to  the  bobbins.  J.  H.  du  Vivier,  Br.  Pat.  2570,  A.  D.  1889, 
prepares  three  solutions  as  follows :  — 

1.  A  12.5  per  cent,  solution  of  gutta  percha  in  carbon  bisulphide. 

2.  A  5  per  cent,  solution  of  isinglass  in  glacial  acetic  acid. 

3.  A  7  per  cent,  solution  of  pyroxylin  in  glacial  acetic  acid. 
These  are  mixed  in  such  proportion  that  the  resulting  solution 

contains  — 

4  parts  nitrocellulose, 

1  part  isinglass, 

\  part  gutta  percha, 

to  which  is  added  a  little  castor  oil  and  glycerine.  The  thread 
coming  from  the  capillary  aperture  is  led  first  through  a  bath  of 
soda,  then  into  one  containing  albumen,  and  finally  into  a  solution 
of  bichloride  of  mercury  to  coagulate  the  albumen.  It  then  passes 
through  the  vapor  of  carbon  bisulphide  on  its  way  to  the  bobbins, 
and  may  be  treated  with  ammonia  and  alum  in  order  to  sufficiently 
impregnate  it  with  alumina  to  prevent  its  burning  readily.  The 
combustible  nature  of  the  nitrocellulose  renders  the  soda  or  other 
chemical  bath  necessary,  as  the  nitric  acid  is  thereby  removed  in 
greater  part.  Chardonnet  employs  a  bath  of  nitric  acid  of  Sp.  Or. 
1.32,  the  temperature  of  which  is  slowly  allowed  to  fall  from  35°  to 
25°,  by  which  means,  it  is  stated,  the  fibre  is  denitrated  and  reduced 
to  the  condition  of  ordinary  cellulose. 

This  new  fibre  promises  to  have  an  important  bearing  on  the 
textile  industries,  as  it  compares  favorably  with  silk  as  to  strength, 
while  surpassing  silk  in  lustre  and  beauty.  Jt  may  be  dyed 
brilliantly  in  any  color. 

Cellulose  and  Chlorine.  —  Dry  chlorine  has  no  effect  upon 
cellulose,  but  when  moisture  is  also  present,  as  when  the  gas  is 
passed  into  water  containing  cellulose  in  suspension,  the  cellulose 
is  rapidly  oxidized  and  carbonic  acid  evolved.  A  similar  action  is 
observed  when  cellulose  is  heated  with  a  solution  of  bleaching 
powder  or  other  hypochlorite.  Cross  and  Be  van  have  lately  shown 
that  in  ordinary  bleaching  there  is  often  some  ehlorinatiuii  of  the 
cellulose.  The  extent  of  the  chlorination  appears  to  depend  some- 
what upon  the  base  present,  and  is  stated  by  them  to  be  conspicu- 
ously less  when  hypochlorite  of  magnesium  is  used  instead  of 
bleaching  powder.  We  find,  in  electric  bleaching,  that  fibre 
caught  and  held  against  the  positive  electrodes  where  it  is  sub- 


CELLULOSE.  113 


ject  to  the  action  of  nascent  chlorine  is  after  some  weeks  con- 
verted into  a  yellow,  gummy  substance,  all  fibrous  structure  being 
lost.  By  acting  upon  guncotton  in  a  sealed  tube  with  phosphorous 
penta-chloride  Baeyer  has  indirectly  prepared  a  compound  of  cellu- 
lose and  chlorine,  which  was  obtained  as  a  viscous  liquid  which 
mixed  readily  with  alcohol  and  ether, 

Cellulose  and  Oxygen  ;  Oxycellulose.  —  The  action  of  oxidiz- 
ing agents  upon  cellulose  has  been  studied  by  Witz,  who  finds  that 
their  first  effect  is  to  convert  the  cellulose  more  or  less  completely 
into  a  white,  friable  substance,  containing  less  carbon  and  more 
oxygen  than  cellulose,  and  for  which  he  has  proposed  the  name 
oxycellulose.  The  frequent  tendering  of  cotton  cloth  in  bleaching, 
or  in  boiling  with  milk  of  lime,  is  due  to  partial  conversion  into 
oxycellulose.  When  cotton  or  linen  cloth  is  wet  with  a  solution 
of  bleaching  powder,  and  exposed  for  some  time  to  the  air,  there  is 
a  gradual  loss  of  strength  and  change  of  composition  as  indicated 
above.  Kept  in  a  very  slightly  acidulated  solution  of  bleaching 
powder  for  several  days,  the  fibre  is  so  completely  changed  to 
oxycellulose  that  it  readily  rubs  down  to  a  white  powder.  When 
converted  into  oxycellulose,  no  reducing  agent,  as  antichlor,  will 
restore  the  fibre  to  its  original  condition. 

Oxycellulose  has  a  powerful  attraction  for  basic  aniline  dyes, 
though  not  for  those  of  acid  character,  and  the  greater  readiness 
with  which  fibre  may  be  colored  after  bleaching  is  due  in  part  to 
the  superficial  formation  of  this  substance.  Many  aniline  blacks 
are  dyed  upon  cloth  which  has  been  partially  converted  into  oxy- 
cellulose and  which  are  consequently  lacking  in  strength. 

Vanadium  salts  are  often  used  in  the  preparation  of  fast  aniline 
blacks,  and  oxycelluloso  has  the  remarkable  property  of  forming 
compounds  with  vanadium  even  in  solutions  containing  only  one 
part  of  the  element  in  1,000,000,000,000.  By  converting  portions 
of  a  fabric  into  oxycellulose  by  the  action  of  oxidizing  agents,  the 
cloth  may  be  dyed  topically  by  dipping  in  a  basic  dyo. 

Fehling's  solution  is  reduced  by  oxycellulose  which  is  colored 
red  by  the  precipitated  copper  oxide.  We  have  noticed  the  for- 
mation of  oxycellulose  in  parchment  paper  held  in  the  wooden 
frames  of  dialyzing  apparatus  used  for  glue  solutions,  the  change 
seeming  to  have  been  induced  by  contact  with  the  slowly  decay- 
ing wood.  Upon  boiling  such  paper  with  Fehling's  solution  the 
copper  oxide  was  deposited  in  streaks,  coinciding  with  the  position 


114  THE  CHEMISTRY  OF  PAPER-MAKING. 

of  the  softer  portions  of  the  grain  of  the  wood.  The  paper  was 
unaffected  where  it  had  not  touched  the  wood. 

Through  the  action  of  more  powerful  oxidizing  agents  than 
those  which  bring  about  the  formation  of  oxycellulose,  cellulose  is 
split  up  into  a  number  of  simpler  molecules.  Treatment  with 
strong  permanganate  or  bichromate  of  potash  gives  glucose,  dextrin, 
and  formic  acid  among  the  decomposition  products.  Hot  chromic 
acid  burns  cellulose  in  the  wet  way,  carbonic  oxide  and  carbonic 
acid  being  formed.  Upon  this  reaction  Cross  and  Be  van  have  based 
a  method  of  ultimate  analysis.  Certain  metallic  oxides,  notably 
iron  rust,  in  contact  with  moist  cellulose,  convert  it  into  glucose 
and  a  gummy  substance  which  changes  to  glucose  on  boiling  with 
dilute  acid. 

Hydrocellulose. : —  When  cellulose  is  moistened  with  any  dilute 
mineral  acid  and  then  drie.d,  or  when  it  is  exposed  for  some  time 
to  their  vapor,  it  is  changed  to  a  friable  substance  having  the 
•composition  C^H^Oy,  and  named  by  Girard,  hydrocellulose ;  by 
Witz,  hydracellulose.  Girard  has  shown  that  the  modification 
thus  brought  about  in  cellulose  is  one  of  true  hydration,  since 
pure  cotton  treated  for  five  days  with  pure  dry  hydrochloric  acid 
gas  showed  no  trace  of  change,  while  it  was  rapidly  converted  to 
hydrocellulose  in  the  presence  of  moisture  and  the  acid.  Liquid 
organic  acids  also  modify  cellulose  considerably,  but  not  to  so  great 
an  extent  as  do  mineral  acids.  Hydrocellulose  is  soluble  in  warm 
potash  lye.  It  absorbs  oxygen  when  heated,  even  at  so  low  a 
temperature  as  50°,  and  after  being  kept  for  some  hours  at  80°  to 
100°  in  contact  with  the  air  is  converted  into  dark  ulinic  com- 
pounds, which  are  soluble  in  water.  Hydrocellulose  does  not,  like 
oxycellulose,  attract  basic  aniline  dyes,  but  both  these  substances, 
like  cellulose,  form  explosive  nitrates  when  treated  with  the 
mixed  acids. 

In  the  process  of  removing  burrs  from  wool,  and  cotton  fibre 
from  mixed  goods,  the  materials  are  moistened  with  dilute  sul- 
phuric acid  and  dried,  by  which  treatment  the  cellulose  is  con- 
verted into  hydrocellulose,  which  from  its  brittle  nature  may  be 
separated  by  mechanical  means.  It  is  sometimes  dissolved  out  by 
weak  alkali,  the  wool  in  either  case  being  unaffected.  A  strong 
solution  of  aluminum  chloride  has  recently  been  used  to  replace 
the  dilute  acid  in  the  "  carbonizing  "  process. 


CELLULOSE.  115 


Water  at  High  Temperatures.  —  The  effect  of  heat  upon 
cellulose  is  greatly  increased  by  the  presence  of  water,  the  cellu- 
lose being  partially  decomposed  with  formation  of  carbonic  acid 
and  dark  brown  products  of  acid  character.  Mulder  was  the  first 
to  observe  the  formation  of  a  small  quantity  of  glucose  at  the 
same  time.  By  extracting  pure  filter  paper,  under  pressure  in  a 
Miincke's  digester,  Tauss  obtained  yellow  extracts  passing  into 
brown  on  exposure  to  the  air,  and  depositing  on  evaporation  a 
black  resinous  precipitate,  soluble  in  alkalis.  Three  hours7  treat- 
ment at  75  pounds  pressure  gave  an  extract  containing,  per  100 
grams  of  cellulose,  1.385  grams  total  solids,  of  which  0.1285 
grams  were  glucose  or  similar  reducing  sugars.  Cellulose,  under 
about  300  pounds  pressure,  was  completely  changed  to  a  jelly-like 
mass,  which  could  be  powdered  after  drying.  Its  composition  was 
then  the  same  as  that  of  hydrocellulose,  C^H^On. 

The  manufacture  of  chemical  fibre  by  the  soda  process  proves 
that  the  action  of  hot  and  moderately  strong  solutions  of  the 
alkalis  has,  at  most,  only  a  superficial  action  upon  cellulose. 
Concentrated  solutions,  Sp.  Gr.  about  1.3,  cause  cellulose  to  swell 
up  and  become  transparent  in  much  the  same  way  that  it  does  in 
the  preparation  of  parchment  paper.  Cloth  thus  treated  and 
washed  free  from  alkali  is  said  to  be  Mercerized,  from  Mercer,  who 
first  prepared  it.  The  cloth  shrinks  considerably  in  the  operation, 
but  acquires  additional  strength.  The  mercerized  cellulose  also 
shows  a  greater  tendency  than  before  to  absorb  water.  Gladstone, 
using  soda-lye  of  Sp.  Gr.  1.342,  has  noted  the  formation  of  a  com- 
pound of  soda  and  cellulose,  C^H^Oio  -h  NaOH,  which  is  resolved 
by  carbonic  acid  or  even  by  washing  with  water.  When  equal 
parts  of  potassium  hydrate  and  cellulose  are  moistened  with  water 
and  heated  in  a  closed  vessel,  hydrogen,  methyl  alcohol,  and  wood- 
spirit  are  driven  off,  while  carbonic,  formic,  and  acetic  acids  are 
found  in  combination  with  the  potash.  Heated  in  contact  with  the 
air  the  main  product  is  oxalic  acid. 

Cellulose  is  decomposed  by  various  fermentative  processes, 
especially  those  going  on  in  the  digestive  canal.  It  is  dissolved 
with  liberation  of  marsh  gas,  by  the  fluid  from  the  vermiform 
appendix  of  the  rabbit.  In  the.  rumen  and  large  intestine  of 
herbivora  it  is  decomposed  into  fatty  acids  and  gases,  consisting 
mainly  of  carbonic  acid  and  hydrogen.  This  has  been  shown  in 
the  laboratory  by  Tappeiner,  who  placed  cotton-wool  in  flasks 


116  THE  CHEMISTRY  OF  PAPER-MAKING. 

with  Nageli's  salt  solution  and  asparagine.  Upon  addition  of 
fluid  from  the  rumen,  fermentation  set  in,  with  evolution  of  volatile 
acids,  hydrogen  and  carbonic  acid. 

In  nature,  when  the  supply  of  air  is  somewhat  limited  and 
moisture  is  present,  cellulose  gradually  decays  with  formation  of 
large  quantities  of  marsh  gas  and  the  dark  brown  or  black  amor- 
phous substances  which  constitute  vegetable  mould  or  humus. 
This  consists  mainly  of  acid  products,  soluble  in  alkaline  solutions. 
Among  them  have  been  recognized  ulmin  and  ulmic  acid,  humin 
and  humic  acid.  This  decomposition  has  an  important  bearing 
on  the  character  of  the  soil,  not  only  through  the  mechanical 
action  of  the  evolved  gases  in  loosening  the  soil,  but  by  the  power 
possessed  by  humus  of  fixing  atmospheric  nitrogen  in  a  form  suit- 
able for  plant  life  (Storer). 

A  peculiar  fermentation,  called  Cellulosic  fermentation,  which 
Durin  first  observed  in  beet  juice  possesses  much  interest  in  con- 
nection with  the  study  of  cellulose.  It  is  there  due  to  a  ferment 
very  similar  to  diastase,  but  may  be  induced  in  solutions  of  cane 
sugar  through  the  influence  of  certain  fatty  seeds,  as  rape  and  colza. 
It  results  in  the  formation  of  hard,  white,  warty  lumps,  which  ex- 
hibit all  the  reactions  of  cellulose,  while  from  the  mother-liquor 
there  is  precipitated,  on  the  addition  of  alcohol,  another  body, 
similar  to  cellulose  in  composition,  but  tough  and  glutinous.  Upon 
placing  some  of  these  lumps  in  a  solution  of  cane  sugar  the  forma- 
tion of  cellulose  continues  at  the  expense  of  the  sugar,  the  solution 
finally  containing  only  a  trace  of  that  substance.  It  has  been  shown 
in  case  of  many  plants  whose  juices  are  rich  in  sugar,  that  as  the 
cellulose  increases,  the  sugar  lessens  in  amount,  and  there  is  little 
doubt  that  in  general  cellulose  is  formed  in  the  living  plant  from 
sugar  and  substances  of  similar  composition  in  the  sap.  Such  food 
as  the  plant  stores  or  holds  in  reserve  is  elaborated  in  the  form  of 
starch,  which  may  be  then,  possibly  by  the  action  of  ferments, 
converted  into  sugar  or  its  isouiers,  to  be  dissolved  and  carried  by 
the  sap. 


FIBRES.  117 


CHAPTER  II. 

FIBRES. 

The  Vegetable  Cell.  —  The  unit  of  structure  in  the  plant  is  the 
vegetable  cell.  All  living  cells  consist  essentially  of  protoplasm^ 
which  in  the  higher  plants  is  surrounded  by  a  wall  of  cellulose,  pro- 
duced by  the  protoplasm  at  the  limiting  film,  and  laid  down  in  close 
contact  with  the  film.  The  protoplasm  is  to  be  regarded  as  the 
actual  basis  of  the  life  of  the  plant,  as  indeed  it  is  the  actual  basis 
of  all  life.  Chemically  considered,  it  belongs  to  the  group  of 
albuminous  bodies,  and  is  closely  similar  in  appearance  and  com- 
position to  the  albumen  which  forms  the  white  of  egg.  Under  the 
microscope  the  protoplasm  is  seen  to  maintain  a  constant  circula- 
tion, which  is  rendered  visible  by  the  granules  in  its  substarioe, 
and  by  means  of  which  nutritive  matters  are  brought  from  the  out- 
side to  the  denser  portion,  called  the  nucleus,  while  the  waste 
products  are  carried  to  the  surface  of  the  mass. 

The  green  color  of  plants  is  due  to  the  presence  at  certain  points 
of  a  peculiar  coloring  matter  called  chlorophyll,  or,  more  properly, 
chlorophyll  pigment,  which  is  ass6ciated  with  certain  of  the  denser 
or  more  differentiated  portions  of  protoplasm,  called  chlorophyll 
granules.  The  coloring  matter  is  developed  only  through  the 
action  of  light.  It  is  soluble  in  alcohol,  the  solution  appearing 
green  in  transmitted  and  blood-red  in  reflected  light.  The  chloro- 
phyll granules  are  the  agents  by  which,  under  the  influence  of 
light,  the  plant  decomposes  the  carbonic  acid  always  present  in  the 
atmosphere,  and  assimilates  the  carbon  needed  for  building  up  the 
plant-structure. 

It  is  only  in  very  young  cells  that  the  cell-wall  consists  of  pure 
cellulose,  and  even  here  it  contains  a  trace  of  mineral  matters. 
With  increasing  age  various  changes  in  the  wall  take  place,  either 
through  degradation  of  the  cellulose  itself,  or  more  generally  by 
the  infiltration  of  other  substances  upon  it.  Through  the  deposi- 
tion of  silica  upon  or  within  the  cell-wall  the  wall  may  be  so 
hardened  arid  stiffened  that  the  change  is  called  mineralization. 


118  THE  CHEMISTRY   OF  PAPER-MAKING. 

Calcium  salts  are  sometimes  so  deposited,  and  well-defined  crystals 
of  the  oxalate  or  carbonate  are  not  infrequently  formed  within  the 
cell. 

Either  with  or  without  these  mineral  matters  there  is  often  a 
deposition  upon  the  cell-wall  of  suberin,  or  cork  substance.  The 
cell  thereby  gains  greatly  in  elasticity  and  such  suberized  cells  are, 
as  would  be  expected,  much  less  permeable  to  water  and  gases  than 
the  normal  cells. 

lagnin. —  By  far  the  most  important  change  which,  from  our 
present  point  of  view,  occurs  in  the  cell-wall  is  that  known  as 
lignification,  and  caused  by  the  formation  and  infiltration  upon 
the  wall  of  a  substance  somewhat  analogous  to  cellulose  and 
called  lignin.  Lignin,  which  probably  consists  of  several  closely 
related  substances,  forms  by  far  the  greater  portion  of  the  incrust- 
ing  matters  which  it  is  the  object  of  several  of  the  preparatory 
processes  of  paper-making  to  remove.  These  changes  do  not 
always  extend  throughout  the  cell-wall,  but  often  only  definite 
layers  or  strata  of  the  wall  are  thus  affected.  The  numerous 
researches  of  Cross  and  Bevan  have  led  them  to  regard  the  lignified 
cell-wall  as  a  chemical  whole,  from  which  by  appropriate  processes 
cellulose  may  be  reduced.  We  are  ourselves  disposed  to  adhere 
to  the  older  view,  which  considers  the  incrusting  matter  as  some- 
thing laid  down  in  intimate  contact  with  the  cellulose  of  the  wall, 
which  itself  remains  unchanged,  and  reappears  when  the  incrustiug 
matters  are  removed  by  solvents.  Contrary  to  the  statement  of 
Erdmann,  and  in  support  of  our  belief,  we  find  that  Schweitzer's 
reagent  readily  removes  the  cellulose  from  lignified  wood-ct  Us. 
The  solution  dissolves  over  35  per  cent,  of  beech,  spruce,  gumwood, 
and  birch  after  they  have  been  extracted  with  water,  alcohol,  and 
ether.  After  boiling  the  extracted  and  washed  residue  with  dilute 
hydrochloric  acid  enough  more  of  the  wood  is  dissolved  by  the 
Schweitzer  reagent  to  bring  the  total  quantity  removed  to  over  60 
per  cent,  of  the  dry  wood. 

Compared  with  cellulose  lignin  is  harder  and  more  elastic  and 
absorbs  relatively  little  water.  The  hardness  of  wood  is  generally 
in  proportion  to  the  amount  of  lignin  it  contains.  The  acetic  acid 
produced  in  the  distillation  of  wood  appears  to  be  derived  chiefly 
and  the  wood-spirit  wholly  from  lignin.  Alkaline  solutions  dis- 
solve lignin  at  a  temperature  of  130°  C;  with  formation  of  acid 
products.  Fused  with  caustic  potash  it  is  converted  into  ulmic 


FIBRES.  119 


acid.  Treatment  with  oxidizing  agents,  as  chlorine,  bromine, 
chromic  acid,  permanganate  of  potash,  or  dilute  nitric  acid,  con- 
verts lignin  into  resinous  acids,  soluble  in  dilute  alkali,  or  the 
oxidation  may  even  proceed  to  the  formation  of  carbonic  acid  and 
water. 

A  solution  of  aniline  sulphate  in  water  or  alcohol  stains  lignin 
yellow ;  nitric  acid  produces  a  yellowish  brown  coloration ;  phloro- 
glucin  gives  a  rose-red  stain  when  the  specimen  has  been  previ- 
ously treated  with  hydrochloric  acid;  a  solution  of  indol  produces 
a  similar  effect  upon  lignified  tissues  which  have  first  been  moist- 
ened with  dilute  sulphuric  acid,  made  by  mixing  one  part  of 
strong  acid  with  four  of  water.  All  of  these  reagents  are  of  much 
value  for  detecting  the  presence  of  incrusting  matters  in  paper- 
making  fibres,  or  in  the  finished  product.  Comparative  tests  may 
easily  be  arranged  to  show  the  thoroughness  with  which  the  boil- 
ing operation  has  been  conducted  in  the  manufacture  of  wood 
fibre,  the  depth  of  color  produced  by  the  reagent  being  in  a 
measure  proportional  to  the  amount  of  incrusting  matter  still 
remaining  in  the  fibre. 

The  chemical  composition  of  lignin  is  still  a  matter  of  some 
doubt.  It  is  known  to  contain  more  carbon  than  cellulose, 
and  Fremy  gives  the  formula  CigH^Og,  while  Schuppe  finds  it  to 
be  C19H18O8.  Although,  as  previously  stated,  lignin  is  probably 
made  up  of  several  analogous  bodies,  it  may,  for  practical  purposes, 
be  regarded  as  a  single  substance,  and  will  be  so  referred  to  by  us. 
Payen  distinguishes  four  different  components,  thus :  — 

Lignose. —  Insoluble  in  water,  alcohol,  ether,  and  ammonia; 
soluble  in  caustic  soda  and  potash. 

Lignin.  —  Insoluble  in  water  and  ether;  soluble  in  alcohol, 
ammonia,  caustic  potash,  and  soda. 

Lignone.  —  Insoluble  in  water,  alcohol,  ether ;  soluble  in  am- 
monia, caustic  potash,  and  soda. 

Lignireose.  — Soluble  in  all  the  above  reagents,  but  only  slightly 
so  in  water. 

Their  percentage  composition,  according  to  the  same  author,  is 
as  below :  — 

Curbou.  Hydrogen.  'Oxygen. 

Lignose    .  .  .  46.HO  6.09  47.81 

Lignin      .  .  .  62.25  5.93  31.82 

Lignone  .  .  .  50.10  5.82  44.08 

Lignireose  .  .  37.91  6.89  25.20 


120  THE  CHEMISTRY  OF  PAPER-MAKING. 

The  thickening  of  the  cell-wall,  which  is  the  result  of  the  deposi- 
tion of  lignin  upon  the  cellulose,  and  which,  up  to  a  certain  point, 
accompanies  increase  of  age,  does  not  in  most  cases  take  place 
uniformly  over  the  entire  surface  of  the  wall.  As  a  consequence, 
depressions  or  markings,  having  in  different  instances  the  form  of 
pits,  lines,  rings,  or  spirals,  appear  in  the  gradually  thickening 
walU  and  often  become  so  distinct  and  characteristic  as  to  afford 
one  of  the  best  means  for  the  identification  of  the  fibres  in  which 
they  occur.  Diffusion  of  sap  and  water  cr  gases  proceeds  with 
greatest  freedom  at  these  thinnest  portions  of  the  wall. 

The  formation  of  gums  and  resins,  although  not  wholly  under- 
stood, is  doubtless  due  to  changes  of  degradation  in  the  cell-wall. 
The  products  may  either  be  found  as  minute,  irregularly  shaped 
drops  within  the  cell  itself,  or  in  the  spaces  formed  by  the  break- 
ing down  of  several  cells,  or,  as  in  the  case  of  spruce  and  other 
coniferous  trees,  in  distinct  receptacles,  known  as  resin-passages. 
The  resins  are  soluble  in  alcohol  and  in  alkaline  solutions,  and  are 
stained  yellow  by  tincture  of  alcannet  root.  They  may  be  distin- 
guished under  the  microscope  by  their  appearance  and  these 
reactions. 

Protoplasm  is  found  only  in  the  living  cells,  and  these  are  at 
the  points  of  growth.  Where  protoplasm  is  absent,  growth  has 
ceased,  and  such  older  lifeless  cells  generally  contain  only  air  more 
or  less  highly  rarefied.  In  some  cases  they  contain  water  or  a 
few  granules.  Their  usefulness  to  the  plant  has  by  no  means 
ceased,  however,  for  from  them  the  plant-structure  derives  in  the 
main  its  strength  and  stiffness.  The  different  plant-cells  present 
an  almost  infinite  variety  of  form,  but,  except  in  case  of  those 
which  serve  as  a  means  of  identification  for  the  fibres  which  they 
accompany,  we  shall  endeavor  to  confine  ourselves  to  those  long- 
drawn,  pointed  elements  of  the  bast  and  wood,  which  are  properly 
called  fibres,  and  which  alone,  with  the  single  exception  of  cotton, 
possess  a  practical  interest  for  the  paper-maker.  They  are  derived 
from  the  ordinary  primitive  cells  by  progressive  growth  and  change 
of  form. 

The  fibres  which  are  commonly  used  in  paper-making  may  be 
divided,  according  to  their  relations  to  the  plant  from  which  they 
are  derived,  into  four  classes. 

1.  Seed-hairs,  as  cotton,  which  is  the  only  representative  of  the 
class. 


FIBRES.  121 


2.  Bast-fibres,  as  linen,  jute,  manila,  adansonia. 

3.  Those  derived  from  whole  stems  or  leaves,  and  associated 
with  various  vessels  and  cells  not  properly  fibres,  as  straw,  esparto, 
sorghum,  bamboo. 

4.  Those  derived  from  wood. 

1.  Seed-Hairs, 

Cotton  (G-ossypium).  —  All  of  the  many  known  varieties  are 
derived  from  the  three  species,  Cr.  Barbadense,  sea-island  cotton, 
which  has  a  very  soft,  silky  staple  nearly  two  inches  in  length ; 
G-.  herbaceum,  upland  or  short  staple  cotton ;  G.  arboreum,  which 
sometimes  attains  the  height  of  a  small  tree. 

The  cotton  fibre  consists  of  a  single  slender  cell  or  hair,  the 
hairs  forming  the  covering  of  cotton  seeds.  The  length  of 
the  fibre  varies  from  2-5  cm.;  diameter,  from  0.012-0.037  mm. 
The  widest  are  found  in  upland  cotton  of  short  staple  ;  the  aver- 
age for  sea-island  cotton  is  0.023  mm.  The  ripe  fibre  presents  the 
appearance  of  a  collapsed  tube  spirally  twisted;  the  unripe  cells 
show  little  or  no  twist.  See  Plate  I.  24-29.  Ordway  mentions  a 
single  fibre  which  had  a  breaking  weight  of  149.4  grains. 

Schunck  has  found  in  raw  cotton  two  coloring  matters:  (a) 
soluble  in  alcohol,  insoluble  in  ether;  (6)  insoluble  in  cold  alcohol, 
soluble  in  boiling  alcohol;  both  containing  nitrogen.  He  has  also 
found  a  wax  similar  to  camauba  wax;  pectic  acid;  albuminous 
matter,  and  a  solid  crystalline  fatty  acid.  All  of  the  above  are 
soluble  in  solutions  of  the  alkalis  and  alkaline  carbonates.  Miiller 
has  analyzed  the  raw  fibre  with  result  as  below :  — 

Per  cent. 

Water     .     .     .     .     .     . 7.00 

Cellulose 91.35 

Fat 0.40 

Aqueous  extract  (containing  nitrogenous 

substances) 0.50 

Ash 0.12 

Cuticular  substance  (by  difference)    .     .  0.63 

2.  Bast-Fibre*. 

The  term  bast  was  first  applied  to  the  inner  bark  of  the  bass- 
wood,  and  later  was  extended  to  include  the  inner  bark  of  other 
plants.  The  long,  tough  cells  found  in  such  barks  were  called 


122 


THE  CHEMISTRY  OF  PAPER-MAKING. 


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FIBRES.  123 


bast-fibres.  Similar  cells  occur,  however,  throughout  other  portions 
of  many  plants,  arid  all  such  cells  are  now  collectively  termed 
bast-fibres  or  liber-fibres.  By  far  the  greater  number  of  the  fibres 
in  use  throughout  the  world  belong  to  this  class. 

The  walls  of  bast-fibres  are  generally  much  thickened  through 
lignification,  and  crystals  are  often  present  in  the  cavity.  The 
thickening  is  often  very  uneven  and  may  cause  projections  of  the 
wall,  within  the  cell.  There  are  also  in  the  different  fibres 
such  considerable  variations  in  the  extent  of  lignification,  and  in 
the  kind  and  quantity  of  foreign  substances  deposited  on  and  in 
the  wall,  that  the  behavior  of  the  fibres  with  reagents  is  often 
sufficiently  characteristic  to  serve  roughly  for  their  identifica- 
tion. 

The  length  of  the  single  fibres  is  seldom  sufficiently  great  to 
permit  their  use  in  textile  manufactures,  and  their  peculiar  value 
for  such  purposes  lies  in  the  fact  that  as  they  occur  in  the  plant 
they  are  associated  together  to  form  bundles,  which  often  attain 
great  length.  We  shall  reserve  the  name  filaments  for  these  bun- 
dles, to  distinguish  them  from  the  ultimate  fibres  of  which  they 
are  composed.  The  fibres  are  generally  firmly  attached  to  those 
immediately  above  and  below  them  by  partial  identity  of  their 
walls,  or  by  incrusting  matter,  and  in  most  cases  a  chemical  treat- 
ment is  necessary  to  effect  their  separation  from  each  other.  The 
separation  of  the  filaments  from  the  body  of  the  plant  is  brought 
about  in  various  ways,  one  of  the  most  common  being  the  well- 
kno\vn  retting  process  applied  to  flax. 

See  table  on  page  122. 

According  to  the  report  by  Cross  and  Be  van,  on  Indian  fibres  and 
fibrous  substances  exhibited  at  the  Colonial  and  Indian  Exhibition, 
London,  1886,  to  which  we  are  indebted  for  much  of  our  material 
relating  to  these  fibres,  there  are  in  India  over  300  fibre-bearing 
plants,  of  which  over  100  yield  strong  and  useful  fibres,  regularly 
employed  by  the  natives  of  that  country.  As  we  shall  give  in 
many  cases  the  results  of  the  chemical  examination  of  the  fibres 
by  these  chemists,  reference  should  be  had  to  the  subjoined  scheme, 
on  page  124,  which  was  followed  in  their  investigations:  — 


124  THE  CHEMISTRY  OF  PAPER-MAKING. 

Moisture.     Hygroscopic  water  or  water  of  condition. 

SEPARATE  PORTION   TAKEN   FOR  EACH   DETERMINATION   BELOW. 
RESULTS  CALCULATED  IN  PERCENTAGE  OF  DRY  SUBSTANCE. 

Ash Total  residue  left  on  ignition. 

Hydrolysis  (a)  .  .  .  Loss  of  weight  on  boiling  raw  fibre  five  min- 
utes in  one  per  cent,  solution  of  caustic  Soda. 
"  (6)  .  .  .  Loss  of  weight  on  continuing  to  boil  one  hour. 

Cellulose White  or  bleached  residue  from  following 

treatment :  (1)  Boil  in  one  per  cent,  caustic 
soda  five  minutes  ;  (2)  exposure  to  chlorine 
gas  one  hour;  (3)  boil  in  basic  sodium, 
sulphite. 

Mercerizing  ....  Loss  on  treating  one  hour  witji  33  per  cent. 

solution  of  caustic  potash,  cold. 

Nitration  .  .  ,  .  .  .  Weight  of  nitrated  product  obtained  by  treat- 
ment with  mixture  equal  volumes  nitric  and 
sulphuric  acids,  one  hour  in  the  cold. 

Acid  purification  .  .  Raw  fibre  boiled  one  minute  with  acetic  acid 

(20  per  cent.),  washed  with  \Vater  and 
alcohol,  and  dried. 

Carbon  percentage  .  .  The  carbon  in  the  fibre  from  above  determined 

by  combustion. 

Linen  (fibres  of  flax  plant)  (Linum  utitatissimum').  —  The 
plant  yields  7.9  per  cent,  of  fibre,  which  is  separated  by  a  fer- 
mentative process  termed  retting,  and  is  then  called  flax.  The 
fibres  (Plate  I,  51-56)  are  thick- walled  tubes,  showing  knots  or 
septa  at  intervals,  and  often  creases.  The  internal  cavity  is  of 
very  small  relative  diameter.  Filaments  run  entire  length  of  stem. 
Bleached  with  more  difficulty  than  cotton.  Muller  gives  the  fol- 
lowing analyses  of  two  samples  of  heckled  Belgian  flax :  — 

Cellulose 81.99  70.55 

Fat  and  wax 2.37  2.34 

Aqueous  extract 3.62  5.94 

Pectous  substances  ....      2.72  9.29 

Water 8.60  1056 

Ash 70  1.32 

The  figures  obtained  by  Cross  and  Bevan  on  a  sample  of  heckled 
Irish  flax  are  as  follows :  — 


FIBIiES.  125 


Moisture  .  ...  9.1 


Following  percentages  are  on  dry  basis. 

Ash 1.6 

Hydrolysis  (a) 13.3 

«           (6) 22.1 

Cellulose 80.2 

Mercerizing 8.4 

Nitration 125.0 

Acid  purification 4.3 

Carbon  percentage      . 43.2 

As  they  occur  in  bleached  linen  cloth  the  fibres  are  nearly  pure 
cellulose. 

Jute  ( Corchorus  capsularis  and  O.  olitQ-rifUgy.  —  Filaments 
obtained  by  retting  and  maceration  of  stem.  Jute  butts  and  cut- 
tings are  the  stamps.  Much  of  the  fibre  received  by  paper-makers 
in  the  form  of  gunny  bags. 

The  fibres  (Plate  I,  7-10)  are  primarily  bound  together,  forming 
filaments  containing  6-20  fibres.  As  ordinarily  used  in  paper- 
making,  with  only  partial  bleaching,  the  fibres  are  not  completely 
separated,  and  the  resulting  stock  is  therefore  especially  long  and 
strong.  Fibres  are  thick-walled,  highly  lignified,  contain  much 
coloring  matter ;  section  is  polygonal. 

Jute,  as  the  type  of  ligniiied-fibres,  has  been  carefully  studied  by 
Cross  and  Bevan,  who  regard  it  as  a  chemical  whole,  termed  by  them 
ligno-cellulose,  which  splits  up  into  cellulose,  as  one  product,  upon 
treatment  with  appropriate  reagents.  They  find  evidences  of  ligni- 
fication  in  even  the  youngest  fibres.  The  fibre  is  easily  chlorinated 
by  the  moist  gas  or  chlorine  water,  and  then  becomes  bright  yellow, 
which  changes  to  magenta  in  solution  of  sodium  sulphite. 

Composition  of  raw  fibre  (Miiller)  :  — 

First  Quality.      Cuttings  or  Butts. 

Cellulose 63.76  60.89 

Fat  and  wax      .....  0.38  0.44 

Aqueous  extract     ....  1.00  3.89 

Non-cellulose  or  lignin   .     .  24.32  20.98 

Water 9.86  12.40 

Ash  0.68  1.40 


126  THE  CHEMISTRY  OF  PAPER-MAKING. 

From  a  sample  of  unusually  good  quality  Cross  and  Be  van  ob- 
tained figures  as  below :  — 

Moisture 10.3 

Following  percentages  are  on  dry  baste. 

Ash 1.2 

Hydrolysis  (a) ,..    .  :.«    .     15.0 

"  (b)  .     .    .    >    ..•  ......     18.0 

Cellulose.     .......   ......    .    .    75.0 

Mercerizing ,    ...    .     16.0 

Nitration 125.0 

i 

Acid  purification    .........      1.0 

Carbon  percentage 46.5 

Hemp  (Cannabis  sativa).  —  Filaments  run  entire  length  of 
stem,  separated  from  bark  by  process  of  retting.  Fibres  (Plate  I, 
57-62)  much  resemble  linen ;  fine  hairs,  however,  project  from  the 
septa  or  knots.  Walls  very  thick,  not  highly  lignified. 

Composition  of  raw  Italian  hemp  (Miiller)  :  — 

Cellulose 77.13 

Fat  and  wax 0.55 

Aqueous  extract  .........  3.45 

Pectous  substances  ........  9.25 

Water .  8.80 

Ash  0.82 


Many  .other  plants  yield  fibres  to  which  the  name  hemp  is 
applied,  but  they  are  usually  distinguished  as  sunn  hemp,  manila 
hemp,  etc. 

Manila — Manila  hemp — (Musa  textilis) . — Filaments  separated 
by  the  natives  in  the  Philippine  Islands  by  drying  and  scraping 
the  outer  sheath  (leaf  petioles)  of  the  stem  of  the  plant,  which 
is  a  species  of  banana;  further  purified  by  beating  and  washing. 
Each  tree  produces  only  about  one  pound  of  fibre. 

Ultimate  fibres  much  shorter  than  in  hemp ;  cavity  much  more 
conspicuous;  number  of  fibres  in  section  of  filament  much  greater; 
section  of  fibre  mow  or  less  polygonal. 


FIBRES.  127 


Composition  of  raw  fibre  (Miiller)  :  — 

Cellulose 64.07 

Fat  and  wax    .              0.62 

Aqueous  extract 0.96 

Lignin  and  pectous  substances  .     .     .     .  21.60 

Water 11.73 

Ash    .............  1.02 

Figures  obtained  by  Cross  arid  Be  van:  — 

Moisture 10,5  per  cent. 

Following  percentages  are  on  dry  basia. 

Hydrolysis  (b) 13.5  per  cent. 

Cellulose. 58.0        " 

Suiiii  Hemp  {Crotalaria  juneea).  —  Filaments,  which  contain 
20-60  fibres,  separated  from  stem  by  retting  as  with  jute.  Fibres 
3-5  mm.  long,  polygonal,  cavity  small,  show  spiral  markings. 
With  iodine  and  sulphuric  acid  fibre  is  colored  a  mixed  blue  and 
brown;  shows  yellow  stains  or  streaks  with  sulphate  of  aniline. 
Sunn  is  not  a  true  hemp,  but  is  derived  from  a  plant  of  the  pea 
family. 

Composition  of  raw  fibre  (Miiller) :  — 

Cellulose 80.01 

Fat  and  wax '    0.55 

Aqueous  extract  .     .     «,     .     .     .     .     .     .      2.82 

Pectous  substances 6.41 

Water 9.60 

Ash 0.61 

New  Zealand  Flax  (Phormiumtenax).  —  Name  flax  mislead- 
ing ;  filaments  are  separated  from  the  leaves,  which,  when  air-dry, 
yield  49.5  per  ceiit  of  cellulose  (Cross),  and  which  attain  a  length 
of  1-2  metres.  Fibres  nearly  white,  soft,  lustrous,  not  highly  ligni- 
fied ;  walls  not  so  thick  as  in  true  flax ;  smooth  ;  no  knots ;  cavity 
much  larger  than  in  flax  (linen). 

Percentage  of  cellulose  in  the  raw  fibre  variously  given  from 
67  to  86:8,  the  higher  figure  being  more  probably  correct. 

Ramie  (Boehmeria  tenacissima).  —  Fibres  stiff;  lustrous  like 
silk ;  take  brilliant  colors ;  sometimes  single ;  average  in  filament 
three ;  section  ovoid  to  polygonal ;  cavity  large.  Separated  with 
some  difficulty  from  plant.  After  separation  bleach  easily. 

Percentage  of  cellulose  75  (Cross). 


128  THE  CHEMISTRY  OF  PAPER-MAKING. 

China  Grass — Rhea — (Boehmeria nivea). —  Not  a  grass,  but  like 
ramie  a  shrubby  plant,  the  filaments  being  derived  from  the  inner 
bark.  General  characteristics  of  ultimate  fibres  similar  to  those  of 
ramie,  but  in  this  species  the  maximum  length  is  much  greater. 
This  is  the  longest  fibre  (ultimate  cell)  known,  the  length  reaching 
220  mm.  (8.66  inches)  in  some  cases.  The  stiffness  of  the  fibre  is 
its  great  drawback. 

Coir  —  Cocoanut  fibre  —  (Cocos  nucifera).  —  Filaments  sepa- 
rated from  the  husk  of  the  cocoanut  by  soaking  for  months  in  water 
and  then  carding.  Has  been  pulped  by  Ekman  in  one  hour,  by  boil- 
ing under  pressure  with  bisulphite  of  magnesia.  Mainly  used  for 
mats,  probably  never  in  practice  as  paper-stock.  Mixed  with  clay 
it  has  been  used  as  an  exterior  coating  for  sulphite  digesters. 

Aclansonia  (inner  bark  of  baobab  or  monkey-bread  tree)  (Adan- 
sonia  diyitata).  —  Has  attracted  some  notice  from  English  paper- 
makers.  Makes  a  strong  paper  which  takes  a  high  finish.  The 
composition  of  the  bast  as  exported  varies,  as  shown  below :  — 

Cellulose     .   ..    .    ,  .v- v    .  49.35  58.82 

Fat  and  wax  .     ...    .     .     .  0.94  0.41 

Aqueous  extract 13.57  7.08 

Pectous  substances  ....  19.05  15.19 

Water    .     .     .    .     .    .     .     .  10.90  13.18 

Ash  .........  6.19  4.72 

Paper  Mulberry  Tree  (Broussonetia  papyrifera). —  The  fibres 
of  the  inner  bark  are  used  by  the  Japanese  in  making  their  peculiar 
paper.  Fibres  are  separated  by  scraping,  soaking,  and  maceration 
in  water ;  are  bleached  in  the  sun,  and  sometimes  further  purified 
by  boiling  in  weak  lye.  The  bark  yields  a  glutinous  substance 
which  acts  as  a  size. 

The  fibres  are  6-20  mm.  long,  soft,  lustrous.  According  to 
Ve*tillart,  they  appear  under  the  microscope  nearly  transparent; 
have  longitudinal  marks  or  striae,  and  are  often  flattened  on  eacli 
other  and  convoluted  like  a  ribbon ;  the  points  p-re  fringed  and 
terminate  in  a  round  end.  They  have  a  tendency  to  curl  up  into 
rings. 

As  they  occur  in  Japanese  paper  the  fibres  are  usually  unbroken. 

The  bark  yields  62.5  per  cent,  of  unbleached  or  58  per  cent,  of 
bleached  fibre  (Routledge). 


FIBRES.  129 


Agave  —  Aloe  —  Century  plant —  (Agave  Americana).  —  Fila- 
ments separated  from  leaves,  by  maceration  or  scraping;  large, 
white,  lustrous,  stiff ;  fibres  2-6  mm.  in  length  (Cross  and  Bevan), 
or  1. 02-2.2  mm.  (Goodale)  ;  walls  thick  ;  cavity  conspicuous ;  sec- 
tion polygonal ;  ends  either  tapering  or  forked. 

Sisal  hemp  or  heniquen  is  derived  from  Agave  ixtli,  common  in 
Yucatan  and  Mexico.  About  one  and  a  quarter  pounds  of  fibre 
are  produced  yearly  by  each  plant.  Largely  used  for  cordage, 
bags,  etc.,  and  comes  in  these  forms  to  the  paper-mill. 

Cross  gives  the  following  figures  on  Agave  Jceratta  from  the 
West  Indies :  — 

Moisture 15.5 

Following  percentages  are  on  dry  basis. 

Ash .    V.  1.4 

Hydrolysis  (a) 10.0 

"           (&) 20.0 

Cellulose 75.8 

Mercerizing      .     .     *  ' 11.0 

Nitration     .  ...    ,    .    .    *    ;     ,    .    .     .  109.8 

Acid  purification 0.4 


Length  of  ultimate  fibres 2-8  min. 

3.   Fibres  derived  from  whole  stems  and  associated  in  the  pulp  with 
cells  and  vessels  not  properly  fibres. 

The  fibres  in  this  class,  although  bast  or  libriform  fibres,  are 
separated  by  treating  the  whole  stem  by  a  chemical  process.  The 
resulting  pulp  consists  of  the  ultimate  fibres,  —  the  filaments  being 
broken  up  in  the  process  of  treatment,  —  and  cells  from  the  epi- 
dermis and  other  portions  of  the  plant. 

Straw  (the  stems  and  leaves  of  the  various  cereals).  —  Straw 
pulp  consists  of  the  ultimate  bast  fibres  and  accompanying  cells, 
freed  from  the  incrusting  and  other  matters  by  a  chemical  proc- 
ess. The  bast  cells  or  fibres  form  the  greater  portion  of  the  pulp. 
They  are  comparatively  short  and  fine ;  at  nearly  regular  intervals 
the  wall  appears  somewhat  thicker  than  elsewhere,  and  drawn 
together  (Plate  I.  30,  31).  The  fibres  and  the  accompanying 
cells  are  stained  blue  by  iodine  solution,  but  these  thickened  por- 


130 


THE  CHSM1STBT  OF  PAPER-MAKING. 


tions  show  a  reddish  brown  coloration.     The  dimensions  of  the 
fibres  from  different  straws  are  given  below :  — 


Wheat 
Bye  . 
Barley 
Oats  . 


Length. 

0.152-0.449  mm. 
0.086-0.345    " 
0.103-0.224    « 
0.186-0.448    « 


Width. 

0.018-0.024  mm. 
0.012-0.016    « 
0.012-0.014    « 
0.012-0.017    « 


The  most  characteristic  feature  of  straw  pulp  is  the  occurrence 
of  epidermal  cells  (Plate  I.  37,  39,  41)  with  serrated  or  toothed 
edges.  These  cells  show  great  differences  in  size,  and  the  propor- 
tion of  length  to  width  varies  from  1:1  to  10 : 1.  The  differences 
are  sufficiently  marked  and  constant  to  enable  the  different  varieties 
of  straw  to  be  distinguished  in  the  pulp.  Associated  with  the 
epidermal  cells  are  others  from  the  pith  (Plate  I.  35,  36),  which 
aid  in  the  recognition  of  this  pulp.  These  cells  vary  in  shape 
from  the  nearly  round  to  an  oval  or  much  more  elongated  form. 
The  width  is  usually  great  in  comparison  to  the  length.  Portions 
of  vessels  and  other  elements  occasionally  occur  (Plate  I.  32,  33, 
34,  40). 

ANALYSES  OF  STRAW   (WOLFF  &  KNOP). 


Winter 
wheat. 

Winter 
rye. 

Winter 
barley. 

Oats. 

Water     

14.3 

14.3 

14.3 

14.3 

Ash     ........... 

5.5 

3.2 

6.6 

6.0 

Albuminoids    •. 

2.0 

1.5 

2.0 

2.5 

Carbohydrates,  etc.  .     .    . 

30.2 

27.0 

29.8 

38.2 

Grade  fibre  .     ....... 

48.0 

54.0 

48.4 

40.0 

Fat,  etc  .    .    . 

1.5 

1.3 

1.4 

2.0 

The  percentage  of  pure  cellulose  in  dry  straw  is  given  by  Cross 
and  Bevan  as  below :  — 

Oat  straw 52.0 

"      " 53.5 

Wheat 49.6 

Eye '.......  53.0 


Arendt  has  exhaustively  investigated  the  composition  of  different 
parts  of  the  oat  plant  at  different  periods  of  growth.    The  straw 


FIBRES.  132 


contains  30-40  per  cent,  of  water  when  fully  ripe,  much  more  if 
cut  earlier.  Straw  is  of  best  quality  if  cut  before  ripening  is  com- 
pleted.  When  about  a  foot  (0.31  m.)  high  both  stem  and  leaves 
contain  about  23  per  cent,  of  crude  fibre  on  the  dry  substance;  at 
commencement  of  ripening  the  stem  contains  36-41,  and  the  leaves 
29-33  per  cent,  of  fibre,  the  proportion  being  in  each  case  lowest 
in  the  upper  part  of  the  plant. 

Straw  yields  a  white  flax  soluble  in  alcohol  and  solutions  of 
caustic  alkali.  •  The  amount  of  ash,  which  is  often  more  than  half 
silica,  ranges  from  about  3-7,  or  in  exceptional  cases  as  high  as 
12  per  cent,  on  the  dry  straw.  The  strongest  straw  yields  the 
moKt  as  ft. 

Esparto  —  Alfa  —  Spanish  Grass.  —  The  rush-like  leaves  of 
Stipa  tenacissima  and  Lygeum  spartum,  which  grow  wild  in  Spat  a 
and  Northern  Africa.  Spanish  esparto  is  considered  the  best. 

The  bast  fibres  occur  in  bundles  or  filaments,  which  are  resolved 
into  ultimate  fibres  by  the  method  of  treatment.  Fibres  (Plate  1. 
43,  49)  similar  to  those  of  straw,  but  shorter,  more  even,  and  with 
cavity  nearly  closed.  Serrated  cells  (Plate  1. 47,  48)  common,  bui 
smaller  than  those  of  straw.  Esparto  pulp  is  distinguished  from 
straw  pulp  by  the  presence  of  small,  tear-shaped  cells  (Plate  I. 
45  Z)  and  the  absence  of  the  oval  cells. 

Miiller  gives  the  composition  of  esparto  as  below :  — 

Spanish.  African. 

Cellulose 48.25  45.80 

Fat  and  wax 2.07  2.62 

Aqueous  extract 10.19  9.81 

Pectous  substances  .     .     ,     .  26.39  29.30 

Water 9.38  8.80 

Ash   . 3.72  3.67 

The  analyses  of  Cross  and  Bevan  give :  — 

Cellulose, 
per  cent,  on  dry  basis. 

Spanish . 58.0 

Tripoli. '  >     .     .     .     .  46.3 

Arzew .  52.0 

Orau    .  ...     .     .     .    .     .     .     .    .     .-     .     .  49.6 

In  paper  esparto  fibre  is  tougher  than  straw.  The  yield  of.  air- 
dry  fibre  on  the  dry  plant  is  from  45-55  per  cent. 


132  THE  CHEMISTRY  OF  PAPER-MAKING. 

Bamboo  (Bambusa). —  About  170  species  are  described  by 
Munro,  Bambusa  vulgaris  being  the  one  most  generally  distributed. 
Mr.  Thomas  Routledge,  who  first  worked  esparto  in  England,  pub- 
lished in  1875  a  pamphlet,  calling  attention  to  the  value  of  bamboo 
as  a  source  of  paper-stock,  and  printed  upon  an  excellent  paper 
made  from  that  material.  Microscopical  examination  of  this 
paper  shows  the  pulp  to  possess  the  general  characteristics  of  that 
from  straw.  The  bast  fibres  are  shov/,  fine,  with  thick  walls; 
serrated  cells  numerous  and  of  various  hapes  and  sizes;  numerous 
ovoid  cells  from  the  pith,  some  nearly  square,  all  pitted.  Cells 
similar  to  those  found  in  esparto  (Plate  I.  45)  and  to  those  shown 
in  Plate  I.  83,  34,  were  also  noticed.  The  proportion  of  these 
different  cells  to  the  fibre  present  is  very  large,  and  from  their 
small  size  many  must  be  lost  in  working  the  pulp. 

The  bamboo  has  been  known  to  attain  a  height  of  forty  feet  in 
forty  days,  and  Routledge  estimates  the  yield  per  acre  at  forty  tons 
of  green  stems,  or  six  tons  of  paper-stock  per  annum.  When  the 
stems  are  cut  before  maturity,  they  are  easily  reduced  by  crushing 
and  boiling  with  caustic  soda. 

Bagasse  and  Sorghum.  —  The  crushed  stalks  and  diffusion 
chips  of  the  sugar  cane  and  sorghum  have  been  often  proposed 
and  occasionally  used  as  a  raw  material  for  paper-making.  They 
are  easily  reduced  by  boiling  with  weak  soda,  and  the  resulting 
pulp  is  much  like  that  from  straw.  On  account  of  the  large  pro- 
portion of  pith  the  yield  of  fibre  is  only  about  25  per  cent,  on  the 
dry  stalk,  and  the  samples  which  we  have  seen  were  so  badly 
specked  by  fragments  of  seed  hulls  as  to  be  useless  for  making  any 
but  the  cheapest  papers. 

4.    Wood. 

The  cells  or  elements  which  make  up  the  woody  tissue  of  plants 
exhibit  great  diversity  of  form  and  markings,  as  is  shown  in  Figs.  3 
and  4  taken  from  Sanio.  Those  which  especially  deserve  consid- 
eration as  furnishing  a  raw  material  for  paper-making  are  the  true 
wood  fibres  and  the  tracJieids.  Many  of  the  other  cells  are,  how- 
ever, of  interest,  as  they  serve  in  some  cases  to  identify  the  wood 
from  which  they  were  derived.  The  wood  fibres  or  libriform  cells 
never  show  true  spiral  markings,  and  the  pits,  which  rarely  occur 
in  the  cell-wall,  are  not  especially  noticeable.  In  certain  of  tliein, 


FIBRES. 


133 


called  septate  cells,  the  cavity  instead  of  being  continuous  through- 
out the  whole  length  of  the  cell,  as  in  most  cases,  is  divided  into 
two  or  more  compartments  by  partitions  perpendicular  to  the 
longer  axis.  The  length  of  the  wood  fibres  and  the  extent  to 
which  their  cell- wall  Anthickened  by  lignification  show  great 
variations  in  different  plants.  Some  of  the  longest  have  a  length 
of  2.0  mm.,  while  others  are  as  short  as  0.14  mm.  ,  Their  arrange- 


:  1 


FIG.  3.  —  WOOD  ELEMENTS  FROM  VARIOUS  PLANTS. 

ment  in  the  plant  stem  also  varies  in  different  cases,  being  some- 
times radial,  and  in  other  instances  showing  an  irregular  grouping. 
Chemical  pulp  made  from  poplar  consists  almost  entirely  of  true 
wood  fibres. 

For  the  practical  purposes  of  paper-making  tracheids  are  to  be 
regarded  as  fibres,  since  they  possess  the  same  elongated  shape 
and  tapering  ends.  They  are,  however,  to  be  distinguished  from 


134 


THE  CHEMISTRY  OF  PAPER-MAKING. 


the  libriform  fibres  by  the  numerous  large  and  well-defined  mark- 
ings, which  from  their  shape  are  called  bordered  pits  or  discoid 
markings.  These  markings  arifce  with  the  gradual  thickening  of 
the  cell-wall  until  finally  they  assume  the?  appearance  shown  in 
Figs.  5,  6,  and  7. 

The  wood  of  cone-bearing  or  coniferous  trees,  like  spruce,  fir,  and 
hemlock,  consists  entirely  of  traehe'ids,  and  4he  discoid  markings 


FIG.  4.  —  WOOD  ELEMENTS  FROM  VARIOUS  PLANTS. 

are  very  apparent  when  sulphite  pulp,  made  from  these  woods, 
is  examined  under  the  microscope.  They  are  even  more  readily 
seen  in  ground  wood.  These  trache'ids  are  much  longer  than 
the  libriform  fibres  occurring  in  the  wood  of  other  trees,  but  in 
the  common  case,  in  which  both  trache'ids  and  fibres  occur  in 
the  same  wood,  the  fibres  are  always  the  longest  elements  in  the 
particular  wood  considered. 


FIBRES. 


135 


Growth  of  Wood.  —  Growth  in  the  widest  sense  takes  place  by 
i:he  division  of  cells.  A  single  cell  is  converted  into  two  by  the 
formation  of  an  excessively  thin  membrane  of  cellulose.  This 


0 


FIG.  5. 

Bordered  pits  or  discoid  markings  of  the  wood  cells  (tracheids)  of  Finns  laricio.: 
a,  aspect  of:  radial  walls ;  b,  a  transverse  section ;  c,  development  of  the  markings 
in  Finns  sylvestris  (Saiiio). 


single  membrane  is  at  first  a  common  wall  for  the  two  adjacent 
cells,  but  as  growth  proceeds  and  the  thickness  of  the  membrane 
increases  it  commonly  splits  into  two  adjacent  walls.  The  growth 
of  wood  depends  upon  the  activity 
of  a  thin  layer  of  tissue  lying  im- 
mediately under  the  bark*  and 
called  the  cambium  layer.  The 
cells  composing;  this  layer  are  filled 
with  protoplasm,  and  by  their  sub- 
division and  growth  new  wood  is 
formed  upon  the  old  wood  in  con- 
centric rings  or  layers.  As  growth 
altogether  ceases  during  winter, 
and  as  the  character  of  the  wood 
produced  varies  periodically  at  dif- 
ferent seasons  of  the  year,  these 
rings  become  visible,  and  serve  as  a  register  of  the  annual  growths. 
The  fibres  and  tracheids  formed  during  the  spring  have  compara- 


Fio.  6. 


Pinus  sylvestris.  Transverse  sections 
of  perfect  and  nearly  perfect  discoid 
markings  (Strasburger). 


136 


THE  CHEMISTRY  OF  PAPER-MAKING, 


tively  thin  walls,  and  are  somewhat  larger   than  those  formed 

during  the  autumn. 

Autumnal  wood  is  somewhat  more 
dense  and  contains  more  incrusting 
matter  than  spring  wood.  A  section 
through  the  wood  shows  that  the  au- 
tumnal fibres  are  considerably  flattened 
by  the  pressure  of  the  bark,  which  is 
greatest  at  this  time,  while  the  section 
of  the  fibres  formed  in  the  spring  is 
nearly  square,  as  shown  in  Fig.  8. 

Sap  and  Heart  Wood.  —  The  wood 
of  comparatively  recent  growth,  or  sap- 
wood,  often  called  from  its  color  albur- 
num, contains  a  larger  proportion  of 
sap  and  putrescible  matters  than  the 

Portion    of    wood-cell    (trache'id)       u  11.11  ^  i 

showing  bordered  pits :  a,  aspect   older  and  harder  heart-wood  or  dura- 

of  radial  wall ;  b,  section  through 


wall  (Herzberg). 


men,  so  called  on  account  of  this 
greater  hardness  and  durability.  The 
difference  in  color  and  hardness  is  not 
always  evident,  as,  for  example,  in  the 
fir  and  sweet  buckeye.  Each  year  a  ring 
of  sap-wood  passes  over  into  the  con- 
dition of  heart-wood,  and  then  takes  no 
further  part  in  the  activity  of  the  plant. 
It  becomes  darker  by  the  infiltration  of 
coloring-matter.  The  thickness  of  the  sap- 
wood  is  practically  constant,  while  that  of 
the  heart-wood  increases  with  each  succeed- 
ing year.  Heart  wood  is  for  most  pur- 
poses of  much  greater  value  than  sap-wood, 
and  when  ground  into  pulp  should  be  less 
likely  to  deteriorate  with  age  than  pulp 
made  from  sap-wood.  There  is,  however, 
a  prejudice  among  pulp-makers  in  favor  of 
sap-wood,  or  for  the  younger  trees  in  which 
it  is  present  in  greatest  amount,  and  it  is 
quite  probable  that  such  wood,  because  of 
its  smaller  content  of  lignin,  would  be  less  brittle  under  grinding, 
and  would  therefore  yield  a  longer  fibre. 


FIG.  8. 


FIBRES.  137 


The  cells  in  the  earliest  annual  rings  are  considerably  smaller 
than  those  in  the  succeeding  rings,  and  the  increase  in  size  pro- 
ceeds regularly  until  after  a  number  of  years  a  maximum  is 
reached  and  maintained  in  the  rings  formed  afterward. 

This  fact  is  brought  out  in  the  following  table  by  Sanio,  quoted  bv 
Goodale,  based  on  measurements  of  trache'ids  of  Pinus  sylvestris :  — 

Number  of  the  annual  Medium  length  of  Medium  width  of 

ring.  the  tracheids.  the  tracheide. 

1 0.95  inm.  0.017  mm. 

17  '.; V-'V-'-.    .  2.74  " 

19 3.13  " 

31  .....     -  3.69  « 

37 3.87  " 

38 3.91  " 

39 4.00  « 

40 4.04    « 

43 4.09  « 

45 4.21  « 

46 4.21  « 

72 4.21  «  0.032mm. 

All  wood  contains  in  the  cell  cavities  a  large  amount  of  air  arid 
water,  the  former  being  highly  rarefied.  According  to  Sachs, 
100  c.c.  pf  freshly  cut  fir  consists  of 

Mass  of  cell-walls 24.81  c.c. 

Water 58.63    « 

Air  cavities 16.56    " 

A  determination  by  ourselves  of  the  amount  of  water  in  green 
spruce  as  received  at  the  mill  gave  37  per  cent,  by  weight.  It  is 
much  larger  in  growing  or  freshly  cut  wood. 

Gelesnoff  determined  the  water  in  entire  trees  each  month  for  a 
year.  Scotch  pine  gave  a  maximum  (January)  of  64.0  per  cent.,  and 
a  minimum  (May)  of  55.3  per  cent. ;  average  for  the  year  61.1  per 
cent.  Aspen  gave  a  maximum  (March)  of  56.6  per  cent.,  and  a 
minimum  (May)  of  48.9  per  cent.;  average  for  the  year  52. 8 per 
cent.  Birch  gave  a  maximum  (May)  of  65.9  per  cent.,  and  a  mini- 
mum (December)  of  43.5  per  cent. ;  average  for  the  year  49.2. 

The  hardness  and  density  of  wood  is  largely  dependent  upon 
the  amount  of  lignin  which  it  Contains.  The  lignin  not  only 
tends  to  harden  the  cell-walls,  but  also  by  its  presence  lessens  the 
space  within  the  cells  which  might  otherwise  contain  air.  The 


138 


THE  CHEMISTRY  OF  PAPER-MAKING. 


following  table,  compiled  from  the  reports  of  the  Tenth  United 
States  Census,  gives  the  density,  ash,  and  fuel  value  of  the  woods 
commonly  used  for  pulp-making.  The  determinations  were  made 
by  Mr.  S.  P.  Sharpies,  under  direction  of  Professor  Sargeant:  — 


BOTANICAL  NAMB. 

COMMON  NAME. 

Specific 
gravity. 

*ll 
III 

£g* 

Ash, 
per 
cent. 

Heat  unit*  evolved 
by    combustion 
of    one     kilo- 
gramme of  dry 
wood. 

Pinus  Strobus. 

White  pine. 

0.3485 

21.72 

0.12 

4272.69 

Pinus  Banksiana. 

Gray    pine    of 

Canada. 

0.4761 

29.67 

0.23 

— 

Picea  nigra. 

Spruce. 

0.4087 

25.47 

0.30 

3949.37 

Abies  grandis. 

Fir. 

0.3545 

21.97 

0.49 

— 

Abies  Fraseri. 

Balsam. 

0.3565 

22.22 

0.54 

— 

Larix  Americana. 

Tamarack. 

0.7024 

43.77 

0.27 

4182.04 

Populus  grandidentata. 

Poplar. 

0.4632 

28.87 

0.45 

— 

Populus  tremuloides. 

Aspen. 

0.3785 

23.69 

0.74 

429S».3i 

Populus  monilifera. 

Cottonwood. 

0.4494 

28.00 

0.65 

424^.16 

Salix  nigra. 

Willow. 

0.4456 

27.77 

0.70 

— 

Fagus  ferruginea. 

Beech. 

0.7175 

44.71 

0.54 

3896.04 

Acer  dasycarpum. 

Maple. 

0.5269 

32.84 

0.33 

— 

Betaila  alba. 

White  birch. 

0.6160 

38.06 

0.29 

4073.05 

Betula  papyrifera. 

Paper  birch. 

0.6297 

39.24 

0.23 

4101.41 

JEsculus  glabra. 

Buckeye. 

0.4542 

28.31 

0.86 

— 

Liquidainbar  styraciflua. 

Sweet  gum. 

0.5616 

34.99 

0.48 

4016.46 

Taxodium  distichum. 

Cypress. 

0.4084 

24.46 

0.40 

4739.73 

Tsuga  Canadensis. 

Hemlock. 

0.4097 

25.53 

0.48 

4208.58 

Castanea  vulgaris. 

Chestnut. 

0.4621 

28.80 

0.13 

4092.96 

Tilia  Americana. 

Basswood. 

0.4625 

28.20 

0.55 

— 

Robinia  pseudacacia. 

Locust. 

0.7267 

46.22 

0.23 

3890.02 

The  heaviest  wood  found  in  the  United  States  is  black  iron-wood, 
Condalia  /erred,  which  has  a  specific  gravity  of  1.3020,  and  is  also 
remarkable  for  its  large  amount  of  ash,  8.31  per  cent.  The  lightest 
is  Ficus  aurea,  which  has  no  common  name.  Its  specific  gravity  is 
0.2616,  and  ash  5.03  per  cent.  Both  trees  are  found  in  Florida. 

Resins.  —  Although,  as  previously  pointed  out,  the  formation  of 
resins  is  not  fully  understood,  they  are  linowii  to  be  immediately 
derived  from  the  oxidation  of  essential  oils  which  occur  in  the 
tree.  If  the  resins  contain  gum  or  mucilage,  they  are  termed  gum- 
resins,  while  if  they  are  mixed  with  the  essential  oils,  they  are 
variously  called  oleo-resins,  turpentines,  or  balsams.  The  term 
oleo-resin  is  the  more  comprehensive  one,  and  only  such  oleo- 


FIBRES. 


139 


resins  as  contain  benzoic  or  cinnaraic  acid  are,  properly  speaking, 
balsams.  The  well-known  but  misnamed  Canada  balsam  is  a  true 
turpentine.  The  oleo-resins  are  generally  viscous  liquids,  like 
honey,  but  sometimes  occur  as  soft  solids. 

The  resins  are  insoluble  in  water,  difficultly  soluble  in  hot  bisul- 
phite solutions,  readily  soluble  in  alcohol  and  alkaline  solutions. 
They  are  to  be  regarded  as  mixtures  of  several  analogous  bodies, 
and  various  substances  of  acid  character  are  recognized  among  their 
components.  Sylvic  acid,  with  others,  is  found  in  common  rosin. 
Rosin,  often  called  colophony,  is  the  residue  left  on  distilling  off  the 
volatile  oil  (spirits  of  turpentine)  from  the  turpentine  obtained 
from  Southern  pine.  The  color  of  rosin  ranges  from  light  yellow  to 
dark  red,  the  darker  color  being,  at  least  in  part,  a  result  of  the 
increased  temperature  to  which  the  rosin  was  exposed  in  order  to 
drive  off  all  the  spirits  of  turpentine.  The  specific  gravity  of  rosin 
is  usually  about  1.083,  but  the  very  light-colored  varieties  may 
have  a  specific  gravity  of  only  1.040,  while  that  of  the  darkest 
specimens  may  run  as  high  as  1.100.  One  hundred  parts  of  refined 
rosin  will  completely  neutralize  about  eighteen  parts  of  caustic 
potash,  KOH.  According  to  Sargeaut,  the  fuel  value  of  resinous 
woods  is  about  12  per  cent,  higher  than  that  of  those  containing 
little  or  no  resin,  but  the  statement  is  evidently  a  general  one. 

The  quality  of  a  wood  for  pulping,  especially  by  the  acid  proc- 
esses, depends  largely  upon  its  freedom  from  any  excessive  quan- 
tity of  resin,  and  nearly  as  much  upon  the  evenness  with  which 
the  resin  is  distributed.  If  the  resin  is  mainly  localized  at  certain 
points  or  rings,  the  other  portions  of  the  wood  may  be  reduced 
with  comparative  ease,  while  the  more  resinous  portions  still 
remain  hard,  and  largely  increase  the  proportion  of  chips  and  shive 
in  the  pulp.  Ulbricht  has  studied  the  distribution  of  resin  in  the 
spruce  fir,  Abies  exceha^  with  the  result  shown  below.  He  includes 
as  resin  all  matter  soluble  in  alcohol  and  not  in  water. 

PARTS  OF  RESIN  PER   100   OF  WOOD. 


Sap-wood. 

Heart-  wood. 

Entire  wood. 

Winter  

1906 

2299 

18213 

Spring    . 

1.781 

2  041 

1.911 

Summer     

1  987 

2  236 

2  109 

Autumn     .......         . 

2  024 

2  158 

2  137 

140 


THE  CHEMISTRY  OF  PAPER-MAKING. 


We  have  made  determinations  of  the  quantities  of  material 
removed  from  the  following  woods  by  water,  and  by  a  successive 
treatment  with  ether  and  alcohol,  with  results  as  shown.  The 
figures  give  per  cents,  on  the  dry  basis :  — 


Water  —  removes 
gums,     mucilage, 
sugars,  tannin,  etc. 

Ether. 

Alcohol. 

Total    removed    by 
ether  and  alcohol 
—  includes  resins, 
oiib,  waxes,  etc. 

Spruce  .              . 

4.83 

1.67 

1.61 

3.28 

Poplar  .    .     ... 

4.80 

0.85 

1.00 

1.85 

Cottonwood  .    .     . 
Sweet  guin    .     .    . 
Beech   

4.69 
3.39 
2.14 

0.79 
0.30 
0.38 

2.04 
0.55 
0.55 

2.83 
0.85 
0.93 

Yellow  birch  .     .     . 
Cypress     .... 

1.88 
4.22 

0.32 
0.81 

0.65 
0.94 

0.97 
1.75 

The  analyses  of  a  number  of  European  woods  have  been  carried 
much  farther  by  Miiller,  and  from  his  results  we  select  those  of 
especial  interest. 


PROXIMATE  ANALYSES   OF   WOODS. 
HUGO  MULLER  (Die  Pflanzenfaser} . 


Water. 

Soluble  in 
water. 

Soluble  in 
alcohol  and 
benzine. 

Cellulose. 

Incrueting 
matter. 

Inorusting 
matter  for 
every  100 
of  cellulose. 

Black  poplar   .     .     . 
Silver  fir     .... 
Birch      .... 

12.10 
13.87 
12  48 

2.88 
1.26 
2  65 

1.37 

0.97 
1  14 

62.77 
56.99 
55  52 

20.88 
26.91 
28  21 

33.3 

47.2 

KA   Q 

Willow  .     .     . 

11  66 

2  65 

1  23 

fia  72 

OQ  74 

ri  a 

Scotch  pine     .     .     . 
Chestnut     .... 
Linden   

12.87 
12.03 
10  10 

4.05 
5.41 
3  56 

1.68 

1.10 
3  93 

53.27 
52.64 
KQ  OQ 

28.18 
28.82 
on  QO 

52.9 
54.7 
fiS  2 

Beech     .... 

12  57 

2  41 

0  41 

4^  47 

QO  1J. 

C(j  i 

Ebony    .... 

9  4Q 

9  99 

o  54 

00  00 

48  08 

IfiO  ^ 

Bark  and  Knots.  —  Simultaneously  with  the  production  of  a 
layer  of  wood,  through  the  activity  of  the  layer  of  cambium  tissue 
surrounding  it,  there  is  formed  on  the  outside  of  this  tissue  a  layer 


FIBRES.  141 


of  bark,  which  serves  as  a  protective  envelope  to  the  stem.  Cork 
cells,  or  those  upon  whose  walls  has  been  deposited  suberin  or 
cork  substance,  are  admirably  fitted  on  account  of  their  imper- 
meability to  protect  the  underlying  tissues  and  occur,  often  in 
layers,  in  the  bark.  Associated  with  them,  more  especially  in  the 
inner  bark,  are  the  long  bast  fibres  which  give  strength  to  the 
bark.  As  the  bark  increases  in  thickness,  the  outer  layers  become 
more  or  less  completely  cut  off  from  the  underlying  tissue  by 
layers  of  cork  cells,  and,  as  a  result,  this  outer  portion  dries  up  and 
dies,  becoming  sometimes  deeply  fissured  as  the  trunk  expands 
with  growth.  The  bark  is  often  rich  in  tannin  and  coloring  mat- 
ters ;  that  of  hemlock  containing  13-16  per  cent,  of  tannin ;  and, 
on  account  of  the  permanence  of  these  colors  and  the  slight  extent 
to  which  suberin  is  affected  by  reagents,  the  bark  is  only  slightly 
acted  upon  by  the  chemical  processes  for  pulping  wood ;  indeed, 
in  the  sulphite  process  hardly  at  all,  and,  if  present  with  the  chips, 
remains  to  form  black  or  brown  specks  in  the  pulp. 

An  experiment  to  determine  the  shrinkage  of  pulp  wood  in 
barking  gave  result  as  follows :  one  cord  of  green  spruce,  containing 
37  per  cent,  moisture,  and  cut  in  four-foot  lengths,  weighed  4440 
pounds ;  after  barking  the  weight  was  3570  pounds. 

Knots  are  formed  at  the  point  where  a  branch  makes  out  from 
the  stem,  and  consist  of  the  dead  and  dried  tissue,  usually  very 
dense  and  highly  charged  with  coloring  matters.  They  are  partially 
reduced  by  the  soda  process,  but  entirely  resist  the  action  of  the 
reagents  employed  in  the  sulphite  process,  which  usually  fails  even 
to  soften  them  appreciably. 

The  woods  most  commonly  employed  in  the  United  States  for 
the  manufacture  of  ground  wood  and  chemical  fibre  are  spruce 
and  poplar.  A  number  of  other  woods  are  used,  however,  in  con- 
siderable, though  varying,  amounts,  as  the  factors  of  price,  length 
of  fibre,  ease  of  reduction,  and  relation  of  the  mill  to  the  source  of 
supply  may  determine  in  particular  cases.  We  shall  consider 
briefly  these  different  woods  with  reference  to  their  occurrence, 
general  features,  and  availability  for  pulp-making.  Their  specific 
gravity,  ash,  and  fuel  value  have  already  been  given.  The  state- 
ments regarding  the  occurrence  and  general  character  of  the  several 
woods  are  taken  from  the  exhaustive  Report  on  Forest  Trees,  by 
Professor  Sargeant,  in  the  reports  of  the  Tenth  United  States 
Census.  The  scientific  names  by  which  the  different  species  are 


142 


THE  CHEMISTRY  OF  PAPER-MAKING, 


designated  by  different  authors  show  a  lack  of  uniformity  almost 
as  great  as  that  which  prevails  in  common  usage  regarding  the 
common  names.  We  have  therefore  followed  the  nomenclature 
of  the  report  to  which  we  have  just  referred.  The  species  given 
by  no  means  comprise  all  those  which  are  or  may  be  used,  but  are 
to  be  considered  as  typical  of  the  different  sorts  of  wood4 employed. 
Thirty-five  species  of  pine  (P«nw«)  are  enumerated  in  the  report 
quoted  as  found  in  the  United  States. 

Black  Spruce  {Picea  nigra).  —  Newfoundland,  northern  Lab- 
rador to  Ungava  Bay,  Nastapokee  Sound,  Cape  Churchill,  Hudson 
Bay,  and  northwest  to  the  mouth  of  the  Mackenzie  River  and  the 
eastern  slope  of  the  Rocky  Mountains;  south  through  the  northern 
states  to  Pennsylvania,  central  Michigan,  Wisconsin,  and  Minne- 
sota, and  along  the  Alleghany  Mountains  to  the  high  peaks  of 
North  Carolina. 

Wood  light,  soft,  not  strong,  close,  straight  grained,  compact, 
satiny;  bands  of  small  summer  cells  thin,  resinous,  resin  passages 
few,  minute;  medullary  rays  few,  conspicuous;  color,  light  red  or 
often  nearly  white,  the  sap-wood  lighter. 

Easily  reduced  to  a  strong,  long-fibred  pulp  by  the  sulphite  proc- 
ess; with  somewhat  more  difficulty  by  the  soda  process;  pulp 
made  by  the  latter  process  bleached  with  difficulty.  We  have 
made  the  following  analyses  of  different  samples  of  the  ground 
'wood :  — 


A. 

B. 

c. 

11.31 

11.48 

11  20 

Ash    .    »     

0.32 

0.25 

0.30 

Cellulose      

52.96 

6P.08 

52  98 

36.41 

S5-19 

35  46 

100.00 

100.00 

1W.OO 

Gray  Pine  (Pinus  BanksiancC).  —  Bay  of  Chaleur,  New  Bruns- 
wick, to  the  southern  shores  of  Hudson  Bay,  northwest  to  the 
Great  Bear  Lake,  the  valley  of  the  Mackenzie  River,  and  the  east- 
ern slope  of  the  Rocky  Mountains  between  the  fifty-second  and 
sixty-fifth  degrees  of  north  latitude ;  south  to  northern  Maine, 
F,errisburg,  Verniont  (R.  E.  Robinson),  the  southern  shore  of 
Lake  Michigan,  and  central  Minnesota. 


FIBRES.  143 


Wood  light,  soft,  not  strong,  rather  close  grained,  compact; 
bands  of  small  summer  cells  not  broad,  very  resinous,  conspicuous, 
resin  passages  few,  not  large ;  medullary  rays  numerous,  obscure  ; 
color,  clear  light  brown  or,  rarely,  orange,  the  thick  sap-wood 
almost  white. 

Reduced  to  pulp  with  somewhat  more  difficulty  than  spruce; 
fibres  long  as  in  spruce. 

AVliite  Pine — Weymouth  pine  —  (JPinus  strobui). — Newfound- 
land, northern  shores  of  the  Gulf  of  Saint  Lawrence  to  Lake 
Nipigon  and  the  valley  of  the  Winnipeg  River,  south  through  the 
northern  states  to  Pennsylvania,  the  southern  shores  of  Lake 
Michigan,  "Starving  Rock,"  near  La  Salle,  Illinois,  near  Daven- 
port, Iowa  (Parry),  and  along  the  Alleghany  Mountains  to  north- 
ern Georgia. 

Wood  light,  soft,  not  strong,  very  close,  straight  grained,  com- 
pact, easily  worked,  susceptible  of  a  beautiful  polish;  bands  of 
small  summer  cells  thin,  not  conspicuous,  resin  passages  small,  not 
numerous  nor  conspicuous  ;  medullary  rays  numerous,  thin ;  color, 
light  brown,  often  slightly  tinged  with  red,  the  sap-wood  nearly 
white. 

Requires  more  severe  treatment  than  spruce,  but  yields  very 
long,  strong  fibre. 

White  Fir  (Abies  grandis).  —  Vancouver  Island,  south  to 
Mendocino  County,  California,  near  the  coast;  interior  valleys  of 
western  Washington  Territory  and  Oregon  south  to  the  Umpqua 
River,  Cascade  Mountains  below  4000  feet  elevation,  through  the 
Blue  Mountains  of  Oregon  (Cusick)  to  the  eastern  slope  of  the 
Cceur  d'Alene  Mountains  (Cooper),  the  Bitter  Root  Mountains, 
Idaho  (Watson),  and  the  western  slopes  of  the  Rocky  Mountains 
of  northern  Montana  (Flathead  region,  Canby  &  Sargeant). 

Wood  very  light,  soft,  not  strong,  coarse  grained,  compact; 
bands  of  small  summer  cells  broader  than  in  other  American 
species,  dark  colored,  resinous,  conspicuous;  medullary  rays  nu- 
merous, obscure  ;  color,  light  brown,  the  sap-wood  rather  lighter. 

Requires  somewhat  more  severe  treatment  than  spruce,  but 
yields,  very  long,  strong  fibre. 

Balsam  (Abies  Fraseri). —  High  mountains  of  North  Carolina 
and  Tennessee. 

Wood  very  light,  soft,  not  strong,  coarse  grained,-  compact; 
bands  of  small  summer  cells  rather  broad,  light  colored,  jiot  con- 


144  THE  CHEMISTRY  OF  PAPER-MAKING. 

spicuous ;  medullary  rays  numerous,  thin ;  color,  light  brown,  the 
sap-wood  lighter,  nearly  white. 

Occasionally  reduced  by  the  sulphite  process ;  unbleached  fibre 
carries  considerable  pitchy  material,  which  is  likely  to  cause 
trouble  in  mill,  and  which  interferes  with  bleaching.  General 
character  of  fibre  similar  to  spruce. 

For  the  purposes  of  his  process  Mitscherlich  considers  balsam 
and  spruce  identical. 

Hemlock  (Tsuya  Canademis*). — Nova  Scotia,  southern  New 
Brunswick,  valley  of  the  Saint  Lawrence  River  to  the  shores  of 
Lake  Temiscaming,  and  southwest  to  the  western  borders  of  north- 
ern Wisconsin ;  south  through  the  northern  states  to  New  Castle 
County,  Delaware,  southeastern  Michigan,  central  Wisconsin,  and 
along  the  Alleghany  Mountains  to  Clear  Creek  Falls,  Winston 
County,  Alabama  (Mohr). 

Wood  light,  soft,  not  strong,  brittle,  coarse,  crooked  grained, 
difficult  to  work,  liable  to  wind-shake,  and  splinter,  not  durable ; 
bands  of  small  summer  cells  rather  broad,  conspicuous ;  medullary 
rays  numerous,  thin ;  color,  light  brown  tinged  with  red,  or  often 
nearly  white,  the  sap-wood  somewhat  darker. 

General  character  of  pulp  similar  to  spruce,  but  wood  is  reduced 
with  more  difficulty,  and  is  likely  to  cause  chips  if  mixed  with 
spruce. 

L,arch  —  Tamarack  —  Hackmatack  —  (Larix  Americana).  — 
Northern  Newfoundland  and  Labrador  to  the  eastern  shores  of 
Hudson  Bay;  Cape  Churchill,  and  northwest  to  the  northern 
shores  of  the  Great  Bear  Lake  and  the  valley  of  the  Mackenzie 
River  within  the  Arctic  Circle ;  south  through  the  northern  states 
to  northern  Pennsylvania,  northern  Indiana  and  Illinois,  and  cen- 
tral Minnesota. 

Wood  heavy,  hard,  very  strong,  rather  coarse  grained,  compact, 
durable  in  contact  with  the  soil ;  bands  of  small  summer  cells 
broad,  very  resinous,  dark  colored,  conspicuous ;  resin  passages 
few,  obscure ;  medullary  rays  numerous,  hardly  distinguishable ; 
color,  light  brown,  the  sap-wood  nearly  white. 

Reduced  by  sulphite  process  with  some  difficulty;  fibre  some- 
what sticky  from  pitchy  material,  and  requires  a  large  amount  of 
blench.  Wood  if  mixed  with  spruce  is  likely  to  cause  chips. 
Length  of  fibre  comparable  to  spruce. 

Poplar  (Populus  yrandidentata). — Nova  Scotia,  New  Bruns- 


FIBRES.  145 


wick,  and  west  through  Ontario  to  northern  Minnesota;  south 
through  the  northern  states  and  along  the  Alleghany  Mountains 
to  North  Carolina,  extending  west  to  middle  Kentucky  and 
Tennessee. 

Wood  light,  soft,  not  strong,  close  grained,  compact;  medullary 
rays  thin,  obscure  ;  color,  light  brown,  the  sap-wood  nearly  white. 

The  wood  most  commonly  used  by  mills  working  the  soda  proc- 
ess; never  used  by  sulphite  mills,  though  easily  reduced  by 
that  process.  Pulp  from  both  processes  very  easily  bleached. 
Fibre  short  and  soft,  associated  in  the  pulp  with  much  wider 
pitted  cells  (Plate  I.  19). 

Aspeii  (Populus  tremuloides).  —  Northern  Newfoundland  and 
Labrador  to  the  southern  shores  of  Hudson  Bay,  northwest  to  the 
Great  Bear  Lake,  the  mouth  of  the  Mackenzie  River,  and  the  val- 
ley of  the  Yukon  River*  Alaska ;  south  in  the  Atlantic  region  to 
the  mountains  of  Pennsylvania,,  the  valley  of  the  lower  Wabash 
River,  and  northern  Kentuckj^ ;  in  the  Pacific  region  south  to  the 
valley  of  the  Sacramento  River,  California,  and  along  the  Rocky 
Mountains  and  interior  ranges  to  southern  New  Mexico,  Arizona, 
and  central  Nevada. 

Wood  light,  soft,  not  strong,  close  grained,  compact,  not  durable, 
containing,  as  does  that  of  the  whole  genus,  numerous  minute, 
scattered  open  ducts ;  medullary  rays  very  thin,  hardly  distinguish- 
able ;  color,  light  brown,  the  thick  sap-wood  nearly  white. 

Much  resembles  poplar  in  character  of  pulp  and  ease  with  which 
wood  yields  to  treatment. 

Cottonwood  (Populus  moniliferfi).  —  Shores  of  Lake  Cham- 
plain,  Vermont,  south  through  western  New  England  to  Chatta- 
hoochee  region  of  western  Florida,  west  along  the  northern  shores 
of  Lake  Ontario  to  the  eastern  base  of  the  ranges  of  the  Rocky 
Mountains  of  Montana,  Colorado,  and  New  Mexico. 

Wood  very  light,  soft,  not  strong,  close  grained,  compact,  liable 
to  warp  in  drying,  difficult  to  season ;  medullary  rays  numerous, 
obscure ;  color,  dark  brown,  the  thick  sap-wood  nearly  white. 

Much  resembles  poplar  in  character  of  pulp  and  ease  with  which 
the  wood  yields  to  treatment. 

Sweet  Gum  (Liquidambar  styraciflua) .  —  Fairfield  County, 
Connecticut,  to  the  valleys  of  the  lower  Ohio,  White,  and  Wabash 
Rivers,  south  to  Cape  Canaveral  and  Tampa  Bay,  Florida,  south- 
west through  southern  Missouri,  Arkansas,  and  the  Indian  Terri- 


146  THE  CHEMISTRY  OF  PAPER-MAKING. 


tory  to  the  valley  of  the  Trinity  River,  Texas;  in  central  and 
southern  Mexico. 

Wood  heavy,  hard,  not  strong,  rather  tough,  close  grained, 
compact,  inclined  to  shrink  and  warp  badly  in  seasoning,  sus- 
ceptible of  a  beautiful  polish;  medullary  rays  numerous,  very 
obscure ;  color,  bright  brown  tinged  with  red,  the  sap-wood  nearly 
white. 

Easily  yields  to  chemical  processes  a  pulp  of  short  fibre,  much 
resembling  poplar. 

Cypress  (Taxodium  dutichum).  —  Sussex  County,  Delaware, 
south  near  the  coast  to  Mosquito  Inlet  and  Cape  Romano,  Florida, 
west  through  the  Gulf  States  near  the  coast  to  the  valley  of  the 
Nueces  River,  Texas,  and  through  Arkansas  to  western  Tennessee, 
western  and  northern  Kentucky,  southeastern  Missouri,  and  south- 
ern Illinois  and  Indiana. 

Wood  light,  soft,  close,  straight  grained,  not  strong,  compact ; 
easily  worked,  very  durable  in  contact  with*  the  soil;  bands  of 
small  summer  cells  broad,  resinous,  conspicuous  ;  medullary  rays 
numerous,  very  obscure ;  color,  light  or  dark  brown,  the  sap-wood 
nearly  white. 

Easily  reduced  to  pulp  by  sulphite  process,  unbleached  fibre 
rather  dark  in  color,  and  woolly  ;  bleaches  readily,  and  then  much 
resembles  spruce. 

Beech  (Fagus  ferruginea).  —  Nova  Scotia  and  the  valley  of 
the  Restigouche  River  to  the  northern  shores  of  Lake  Huron 
and  northern  Wisconsin,  south  to  the  Chattahoochee  region  of 
western  Florida  and  the  valley  of  the  Trinity  River,  Texas,  west 
to  eastern  Illinois,  southeastern  Missouri,  and  Madison  County, 
Arkansas  (Letterman). 

Wood  very  hard,  strong,  tough,  very. close  grained,  not  durable 
in  contact  with  the  soil,  inclined  to  check  in  drying,  difficult  to 
season,  susceptible  of  a  beautiful  polish;  medullary  rays  broad, 
very  conspicuous ;  color  varying  greatly  with  soil  and  situation, 
dark  red,  or  often  lighter,  the  sap-wood  nearly  white. 

Rather  more  difficult  to  reduce  than  poplar  -r  fibres  somewhat 
shorter;  pulp  soft,  easily  bleached. 

Silver  Maple  (Acer  dasycarpuni).  —  Valley  of  the  Saint  John 
River,  New  Brunswick,  to  Ontario,  south  of  latitude  45°,  south  to 
western  Florida;  west  to  eastern  Dakota,  eastern  Nebraska,  the 
valley  of  the  Blue  River,  Kansas,  and  the  Indian  Territory. 


FIBRES.  147 

Wood  light,  hard,  strong,  brittle,  close  grained,  compact,  easily 
worked ;  medullary  rays  numerous,  thin. 

More  difficult  to  reduce  than  poplar ;  fibres  somewhat  shorter ; 
pulp  soft,  easily  bleached ;  rarely  used,  and  only  by  soda  mills. 

Bass  Wood  (Tilia  Americana).  —  Northern  New  Brunswick, 
westward  in  British  America,  to  about  the  one  hundred  and  second 
meridian ;  southward  to  Virginia,  and  along  tne  Alleghany  Moun- 
tains to  Georgia  and  southern  Alabama ;  extending  west  in  the 
United  States  to  eastern  Dakota,  eastern  Nebraska,  eastern  Kansas, 
the  Indian  Territory,  and  southwest  to  the  valley  of  the  San 
Antonio  River,  Texas. 

Wood  light,  soft,  not  strong,  very  close  grained,  compact,  easily 
worked ;  medullary  rays  numerous,  rather  obscure  ;  color,  light 
brown,  or  often  slightly  tinged  with  red,  the  sap-wood  hardly 
distinguishable. 

Very  easily  reduced,  and  yields  by  soda  process  pulp  similar  to 
poplar. 

White  Birch  (Betula  alba).  —  New  Brunswick  and  the  valley 
of  the  lower  Saint  Lawrence  River  to  the  southern  shores  of  Lake 
Ontario ;  South,  generally  near  the  coast,  to  Newcastle  County, 
Delaware. 

Wood  light,  soft,  not  strong,  close  grained,  liable  to  check  in 
drying,  not  durable ;  medullary  rays  numerous,  obscure ;  color, 
light  brown,  the  sap-wood  nearly  white. 

Easily  reduced;  pulp  much  resembles  poplar. 

Paper  Birch  (Betula  papyrifera).  —  Northern  Newfoundland 
and  Labrador  to  the  southern  shores  of  Hudson  Bay,  and  northwest 
to  the  Great  Bear  Lake,  and  the  valley  of  the  Yukon'  River,  Alaska ; 
south  in  the  Atlantic  region  to  Wading  River,  Long  Island,  the 
mountains  of  northern  Pennsylvania,  Clear  Lake,  Montealm 
County,  Michigan,  northeastern  Illinois,  and  Saint  Cloud,  Minne- 
sota ;  in  the  Pacific  region  south  to  the  Black  Hills  of  Dakota  (R. 
Douglas),  the  Mullen  Trail  of  the  Bitter  Root  Mountains  and 
Flathead  Lake,  Montana,  the  neighborhood  of  Fort  Colville, 
Washington  Territory  (Watson),  and  the  valley  of  the  lower 
Fraser  River,  British  Columbia  (Engleman  &  Sargeant). 

Wood  light,  strong,  hard,  tough,  very  close  grained,  compact : 
medullary  rays  numerous,  obscure  ;  color,  brown  tinged  with  red, 
the  sap-wood  nearly  white. 

Somewhat  more  difficult  to  reduce  than  poplar.  Pulp  easily 
bleached  and  similar  to  poplar. 


148  THE  CHEMISTRY  OF  PAPER-MAKING. 

Buckeye  (^Esculus  glabra).  —  Western  slopes  of  the  Alleghany 
Mountains.  Pennsylvania,  to  northern  Alabama,  westward  through 
southern  Michigan  (rare)  to  southern  Iowa,  eastern  Kansas  to 
about  longitude  97°  west,  and  the  Indian  Territory. 

Wood  light,  soft,  not  strong,  close  grained,  compact,  difficult  to 
split,  often  blemished  by  dark  lines  of  decay;  medullary  rays 
obscure  ;  color,  white,  the  sap-wood  darker. 

Said  to  be  occasionally  used  in  pulp-making. 

Black  Willow  (Salix  nigra). — Southern  New  Brunswick  and  the 
northern  shores  of  Lakes  Huron  and  Superior,  southward  through 
the  Atlantic  region  to  Bay  Biscayne  and  the  Caloosa  River, 
Florida,  and  the  valley  of  the  Guadalupe  River,  Texas ;  Pacific 
region,  valleys  of  the  Sacramento  River,  California,  and  the  Colo- 
rado River,  Arizona. 

Wood  light,  soft,  weak,  close  grained,  checking  badly  in  drying  ; 
medullary  rays  obscure ;  color,  brown,  the  sap-wood  nearly  white. 

Said  to  be  occasionally  used  in  pulp-making. 

Locust  (Robinia  pseudacacia).  —  Alleghany  Mountains,  Penn- 
sylvania (Locust  Ridge,  Monroe  County,  Porter),  to  northern 
Georgia ;  widely  and  generally  naturalized  throughout  the  United 
States  east  of  the  Rocky  Mountains,  and  possibly  indigenous  in 
northeastern  (Crowley's  Ridge)  and  western  Arkansas  and  the 
prairies  of  eastern  Indian  Territory. 

Wood  heavy,  exceedingly  hard  and  strong,  close  grained,  com- 
pact, very  durable  in  contact  with  the  ground ;  layers  of  annual 
growth  clearly  marked  by  two  or  three  rows  of  large,  open  ducts  ; 
color,  brown  or,  more  rarely,  light  green,  the  sap-wood  yellow. 

Said  to  be  occasionally  used  in  pulp-making. 

Chestnut  (Castanea  vulyaris).  —  Southern  Maine  to  the  valley  of 
the  Winooski  River,  Vermont,  southern  Ontario  and  southern 
Michigan,  south  through  the  northern  states  to  Delaware  and 
southern  Indiana,  and  along  the  Alleghany  Mountains  to  northern 
Alabama,  extending  west  to  middle  Kentucky  and  Tennessee. 

Wood  light,  soft,  not  strong,  coarao  grained,  liable  to  check  and 
warp  in  drying,  easily  split,  very  durable  in  contact  with  the  soil ; 
layers  of  annual  growth  marked  by  many  rows  of  large,  open 
ducts ;  medullary  rays  numerous,  obsciire ;  color,  brown,  the  sap- 
wood  lighter. 

Said  to  be  occasionally  used  in  pulp-making. 


FIBRES. 


149 


The  following  table,  from  the  report  for  1890  of  the  chief  of  the 
Division  of  Forestry,  gives  interesting  figures  regarding  the  use  of 
the  various  woods  in  palp-making :  — 


States. 

J 

Kinds  of  wood  used. 

Range  of  yield,  per 
cord,  in  hundred  s 
of  pounds. 

Number  of 
mills  re. 
porting 
supplies. 

Remark*. 

I 
"o 

fc 

Mechanical. 

1 

2 

I 

"3 

32 

1 

i. 
2 

3 

M 
= 

.5 

* 

1 

Maine  

12 
7 
1 
1 
13 

2 
11 

5 
1 
4 

4 
1 

52 
4 

1 
1 
2 
2 
1 

1 
1 

2 

2 
2 
1 

1 
2 

1 

1 

2 

1 
3 
1 
1 
1 

1 

Spruce  only  or  chiefly.  .  . 
Spruce  and  poplar  
Spruce,  poplar,  and  pine. 
Poplar  

16-20 
15-20 

io 

11-13.6 

! 

20 

1 
i 

1  gets  supplies  mostly 
from  Canada. 
2  get  supplies  partly 
from  Canada. 
1  gets  supplies  mostly 

2  supplies  fromNorth- 
ern   Vermont   and 
New  Hampshire. 

supplies   from   New 
Brunswick         and 
Nova  Scotia. 
1     supplies     mostly 
from  Canada. 
15  supplies  from  Can- 
ada or  d  istan  t  poi  nt  •. 

Supply    from    West 
Virginia  and  Nova 
Scotia. 
Supply    from    Mary- 
land  and  Virginia. 

S  pruce    from   West 
Virginia   and  Can- 
ada. 

New       Harap 
glare 

Vermont  

Massachusetts. 

Connecticut  .. 
New  York.... 

Pennsylvania.. 

Maryland  

Delaware  
Virginia  
West  Virginia. 
North  Carolina 
South  Carolina 
Georgia  

Kentucky  — 
Ohio  

•  • 

i  " 

10  3 

Spruce  only  or  chiefly  .  .  . 
Spruce  and  poplar  

18-24.5 

10 

10 

11 

i 

4 

• 

3 

Spruce  only  or  chiefly  .  .  . 
Spruce  and  poplar  

18-20 

20-23 
20 
15-22 

17-18 



11 

*"io 

5 

•• 

•' 

Spruce  only  or  chiefly  .  .  . 

Spruce  

34 

7 

8 

2 

2 

Spruce  only  or  chiefly  .  .  . 
Spruce  and  poplar  
Spruce  and  hemlock  

15-22 
16-20 

.... 

13 

11 
10 

Spruce,  hemlock,  bass  .. 

Spruce,  poplar,  and  pine 
Poplar  

14 

9 

TO 

Poplar,  bass,  pine,  and 
spruce. 

Spruce  only  or  chiefly 
Spruce  and  poplar 

19-20 

•\ 

1 

10 

1 
2 

Poplar  

1ft 

Poplar,  bans,  piue  
Poplar,  bass,  pine,  maple 
Hemlock,    pine,    beech, 
bass. 
White  pine  



9-10 
7-1? 



.. 

2 

2 

'i 

2 
2 
1 

i 
i 

i 

16 
18 

10 
10 

io 

1 

1 

1 

1 

Spruce  only  or  chiefly.  .. 

Poplar  

Poplar  
Spruce  only  or  chiefly.  .. 

20 
17 
10 

ib.i 

i 

2 

Cypress  and  gum  •'  . 

Pine  

Cypress  and  gum  ~. 

20-27 

.... 



a 
i 

Spruce,     buckeye,    and 
maple   . 

18 
17 

2 

Spruce  only  or  chiefly.  .  . 
Cottonwood  and  bass  — 

9 

10 

150 


THE  CHEMISTRY  OF  PAPER-MAKING. 


States. 

Number  of  mills. 

Kinds  of  wood  used. 

Range  of  yield,  per 
cord,  in  hundreds 
of  pounds. 

Number  of 
mills  re- 
porting 
supplies. 

Remarks. 

Mechanical. 

I 

Sulphite. 

J 

i 
5 

Limited. 

Declining. 

1 

Indiana  
Michigan     ..  . 

3 
1 

2 
1 

1 
1 
4 

3 
4 

1 

4 
15 
4 
1 
1 
1 

16 
16 
12 
10 

20 

ij 

1 

1 

1    supply    all    from 
Canada. 

1  1 

Poplar,  spruce,  pine  
Aspen,    poplar,    cotton- 
wood. 
Cottonwood     

T 

2 

1 

"'9'  

i 

i 

Spruce  only  or  chiefly  ... 
Poplar  

16 

16-20 

15 

8-10 

i 

2 

2 

1 

Wisconsin  — 
Minnesota  .... 

Poplar,  pine,  tamarack, 
spruce,  and  balsam. 
Aspen,     pine,      poplar, 
spruce,  and  bass. 
Spruce  only  or  chiefly 
Spruce  and  poplar  
Spruce,  poplar,  pine  
Spruce  only  or  chiefly  .  .. 
Cottonwood  

14 

16-18 
13-15 
10-12 
16 

.... 

9-10 
9-10 

2 
5 

'2 

1 
1 

0 

'2 

1 

California  

17 

I 

PROCESSES  FOB  ISOLATING  CELLULOSE.  151 


CHAPTER  III. 

PROCESSES   FOR  ISOLATING   CELLULOSE. 

Rag  Boiling.  —  In  order  to  free  the  rags  from  the  dirt  and  other 
impurities  with  which  they  are  generally  associated  as  received  at 
the  mill,  they  are  put  through  a  preliminary  mechanical  treatment, 
and  are  then  boiled,  usually  under  pressure,  with  alkali.  The  pre- 
liminary treatment  involves  the  threshing,  picking,  cutting,  and 
sorting  of  the  rags,  opening  seams  to  facilitate  removal  of  dirt, 
carefully  removing  all  buttons,  metallic  fasteners,  rubber,  and  such 
foreign  materials,  a  final  cutting  by  machinery  into  pieces  about 
..two  inches  square,  and  dusting.  Such  severe  treatment  is,  of 
course,  unnecessary  in  the  case  of  new  cuttings,  which  contain 
merely  a  moderate  admixture  of  starch,  clay,  and  similar  sub- 
stances employed  in  sizing  and  filling,  and  such  rags  are  often  put 
directly  into  the  engine  and  beaten  up  when  strength  is  especially 
desired. 

The  object  of  the  boiling  operation,  to  which  all  other  rags  are 
subjected,  is  to  bring  the  grease,  dirt,  and  other  impurities  into 
such  condition  that  they  may  subsequently  be  easily  removed  by 
washing,  and  to  destroy  or  so  affect  the  coloring-matter  as  to 
facilitate  the  process  of  bleaching.  Lime  is  only  slightly  soluble 
in  water,  1  part,  in  the  cold,  dissolving  in  425  parts  of  water,  but 
it  forms,  with  the  acids  of  the  grease,  insoluble  soaps,  and  as  these 
are  precipitated,  fresh  portions  of  the  alkali  pass  into  solution.  In 
the  case  of  soda,  the  soaps  formed  are  soluble,  and  therefore  more 
easily  washed --out;  but  the  :uoiion  of  this  base,  in  strong  solution, 
upon  the  fibreiis  more  severe,  and  it  is  believed  to  occasion  greater 
loss. 

The  rotaries  commonly  employed  are  of  the  well-known  cylin- 
drical, horizontal  type,  turning  about  once  a  minute,  and  of  various 
dimensions.  They  are  fitted  with  manholes  and  with  steam-pipes, 
the  latter  passing  through  the  trunnions  and  curving  below  them. 
The  rotary  is  packed  with  rags,  and  milk  of  lime  is  run  in  through 
a  sieve,  which  may  be  made  of  a  piece  of  Fourdrinier  wire;  water 


152  THE  CHEMISTRY  OF  PAPER-MAKING. 

Is  added  in  amount  sufficient  to  come  above  the  journals,  or  even 
in  some  cases  to  fill  the  boiler  two-thirds  full,  the  manholes  are 
closed,  and  in  the  best  practice  the  rotary  is  allowed  to  run  for 
half  an  hour  before  steam  is  admitted.  The  lime  used  should 
contain  as  little  iron  as  possible,  and  is  best  suited  for  this  purpose 
when  the  content  of  magnesia  is  small,  since  this  base  is  practically 
insoluble  in  water,  and  is  much  less  powerful  in  its  action  than 
lime.  The  lime  should  slake  readily  and  completely,  and  should 
be  so  kept  as  to  avoid  air-slaking.  We  give  below  an  analysis  of 
an  excellent  grade  of  lime  for  this  purpose :  — 

Per  cent. 

Silica,  etc.,  insoluble  in  acid ......  0.01 

Iron  and  alumina  (Fe2O3  and  A1208)  .     .     .  0.28 

Lime  (CaO) 92.81 

Magnesia  (MgO) 2.28 

Moisture,  carbonic  acid,  etc.  (by  difference)  4.62 

Total      .    .^_.     .......  lOOOO 

The  proportion  of  lime  used,  as  well  as  the  pressure  and  time  of 
boiling,  depends  very  much  upon  the  character  of  the  rags  treated 
and  the  amount  and  kind  of  dirt  which  they  contain.  From  5  to 
18  per  cent,  of  lime  on  the  bale  weight  of  the  rags  are  the  extremes, 
the  general  tendency  being  toward  the  higher  limit.  For  No.  3 
cottons  and  blues  about  15  per  cent,  of  lime  is  used;  for  shivy 
linen  15  to  18.  A  pressure  of  60  to  80  Ibs.  of  steam  is  usually  car- 
ried, and  thf  time  of  boiling  extends  from  twelve  to  eighteen  hours, 
though  the  details  of  treatment  vary  not  only  with  the  stock,  as 
just  stated,  but  also  in  different  mills.  The  paper-maker  is 
governed  by  the  stock  he  has  and  the  paper  he  has  to  make.  The 
better  grades  of  rags  require  less  time,  pressure,  and  lime,  and  are 
in  many  mills  boiled  in  open  bleaches. 

lii  emptying  the  rotaries  the  practice  also  varies.  Some  super- 
intendents blow  the  pressure  down  completely  before  opening  the 
bottom  blow-off  to  run  off  the  liquor  prior  to  opening  the  man- 
holes ;  while  others,  as~  we  believe  with  good  reason,  reduce  the 
pressure  to  20  or  30  Ibs.,  and  blow  the  liquor  off  under  this 
pressure  through  the  bottom  valve,  claiming  thereby  to  carry  away 
more  dirt.  An  objection  to  this  procedure  is  found  in  the  danger 
of  losing  some  fine  fibre  in  the  blow-off.  As  soon  as  the  liquor  has 
left  the  rags,  they  are  dumped  upon  the  floor  to  drain.  The  empty- 
ing is  performed  with  as  much  expedition  as  possible,  in  order  that 


PROCESSES  FOR  ISOLATING   CELLULOSE. 


153 


the  liquor,  which  contains  substances  more  readily  soluble  in  hot 
than  in  cold  water,  may  carry  these  off  before  it  cools.  The  rags 
are  softened  if  they  are  allowed  to  remain  piled  up  on  the  floor  for 
several  days. 

Japanese  rags  are  washed  and  spread  upon  the  grass  at  the 
country   of  shipment,  and  seed  hulls   thus   derived  may  cause 

LONGITUDINAL.  SECTION. 


FIG.  9.  — THE  MATHER  KIER. 


trouble.  They  may  be  reduced  by  the  addition  of  1  per  cent,  of 
soda-ash  on  the  weight  of  the  rags.  Such  addition  of  soda-ash,  in 
the  proportion  of  1  to  5  per  cent.,  greatly  increases  the  efficiency 
of  the  liquor  in  its  action  upon  certain  colors,  as  for  instance  red, 


154 


THE  CHEMISTRY  OF  PAPER-MAKING. 


which  is  usually  difficult  to  destroy,  and  which  may  even  leave  a 
tinge  of  that  color  in  the  bleached  half-stuff.  Japan  blues  give  a 
bluish  tinge  suitable  for  white  papers,  while  the  darker  shades  of 
natural  may  be  as  well  made  from  city  rags,  which  are  usually 
darker  than  those  from  the  country.  Such  considerations  are 

SECTION 


EIG.  10. — THE  MATHRB  KIER. 

borne  in  mind  by  the  superintendent  in  sorting  and  mixing  the 
rags  prior  to  boiling. 

The  Mather  Kier.  —  This  well-known  apparatus,  which  is 
shown  in  Figs.  9  and  10,  was  originally  designed  for  the  bleaching 
of  textiles,  and  its  adoption  by  the  leading  bleachers  of  cloth  all 


PROCESSES  FOE   ISOLATING   CELLULOSE.  155 


over  the  world  has  demonstrated  its  value  in  this  direction.  It 
lias  lately  been  applied  to  the  boiling  of  rags  for  paper-making  at 
the  mill  of  W.  Joynson  &  Son  in  England,  and  the  results  there 
secured  are  such  as  to  merit  the  attention  of  American  paper- 
makers. 

The  kier  consists  of  a  horizontal  boiler  closed  in  front  by  a 
door,  J?,  which  is  the  full  diameter  of  the  kier.  This  door  is 
balanced  by  the  counterpoise,  6r,  and  is  raised,  lowered,  and  set 
up  against  the  seat  by  hydraulic  power.  On  the  bottom  of  the 
kier  are  tracks  upon  which  can  be  run  in  two  cars,  A,  A,  contain- 
ing the  cloth  or  rags.  Owing  to  the  construction  of  the  kier  and 
the  mode  of  operation  the  amount  of  liquor  required  is  very  small. 
The  liquor  is  drawn  from  the  bottom  of  the  kier  through  D  by  the 
pump,  P,  and  is  discharged  upon  the  rags  through  the  inlets,  (7,  (7, 
above  the  spreaders,  J5,  B. 

The  results  obtained  in  the  treatment  of  rags  in  practice  are  best 
set  forth  in  the  report  of  Messrs.  Cross  and  Bevan,  which  is  given 
in  large  part  below :  — 

A  kier  was  erected  last  year  [1888]  at  the  works  of  Messrs.  W.  Joynson  & 
Son,  St.  Mary  Cray,  where  it  has  been  in  continual  use  for  six  months.  Its 
dimensions  are  8  feet  long  by  7  feet  in  diameter,  and  it  is  adapted  to  hold  two 
wagons.  In  order,  however,  to  economize  time,  six  wagons  are  employed  by 
Messrs.  Joynson,  four  either  being  filled  or  washed,  while  the  other  two  contain 
rags  in  process  of  treatment  in  the  kier.  The  cut  and  dusted  rags  are  delivered 
automatically  from  a  shoot  direct  into  the  wagons.  The  average  weight  taken 
by  each  wagon  is  16  cwt.,  the  full  kier  charge  being  therefore  32  cwt.  The  run- 
ning of  the  wagons  into  the  kier  and  the  closing  of  the  patent  door  occupy  only 
some  two  or  three  minutes.  As  soon  as  this  is  completed,  the  rags  are  saturated 
with  about  750  gallons  of  caustic-soda  solution,  which  is  delivered  from  a  tank 
above  the  kier,  and  is  circulated  by  means  of  a  centrifugal  pump.  Steam  is 
turned  on  until  the  pressure  reaches  10  Ibs.  per  square  inch,  and  the  process 
continued  for  from  two  to  three  hours  according  to  the  nature  of  the  material. 
The  steam  is  blown  off,  which  occupies  about  fifteen  minutes,  the  door  opened, 
the  wagons  removed,  and  another  pair  run  in,  the  three  latter  operations  occupy- 
ing only  ten  minutes. 

The  rags,  after  being  withdrawn  from  the  kier,  are  washed  by  causing  cold 
water  to  flow  on  to  the  top  of  the  wagons.  By  performing  this  operation  out- 
side the  kier  a  considerable  saving  of  steam  is  effected,  only  one  heating  up  of 
the  kier  being  required.  Arrangements  are  provided  for  washing  the  rags  by 
upward  displacement,  by  which  a  further  economy  of  water  is  effected. 

The  kier  in  use  at  Messrs.  Joynson's  is  capable  of  doing  at  least  40  tons  of 
rags  per  week :  it  has,  in  fact,  for  some  time  past  been  used  for  treating  the 
whole  of  the  rags  used  in  the  mill.  It  is  equally  well  adapted,  with  certain 


156  THE  CHEMISTBY  OF  PAPER-MAKING. 

slight  modifications  of  treatment,  for  ail  classes  of  rags,  from  new  linen  and 
cotton  pieces  to  unbleached  linen. 

The  labor  required  is  one  man  for  "  treading  "  the  tags  into  the  wagons,  one 
man  for  tending  the  kier,  mixing  the  liquors,  etc.,  and  one  man  for  emptying 
the  wagons.  Where  circumstances  permit,  the  wagons  can  be  hoisted  and 
transferred  direct  to  the  side  of  the  breaking  engines,  thereby  saving  the  labor 
of  emptying  into  trucks. 

The  following  are  among  the  further  advantages  claimed  for  the  kier,  and 
substantiated  by  the  result  of  the  extended  trial  by  Messrs.  Joynson  &  Son:  — 

1.  The  rags,  being  stationary  during  the  steaming,  are  never  "  knotted,"  as  is  the 
case  with  revolving  boilers;   they  can  therefore  be  rapidly  filled  into  the 
breakers  without  danger  to  the  breaking  rolls. 

2.  A  notable  improvement  in  the  color  of  the  rags,  after  treatment,  both  before 
and  after  bleaching.   This  would  enable  the  paper-maker  to  use  rags  of  some- 
what lower  quality,  without  affecting  the  color  of  his  paper.     If  an  improved 
quality  of  pulp  is  not  so  much  desired  as  economy  of  chemicals,  a  saving 
of  about  25  per  cent,  of  the  latter  can  be  effected.    It  amounts  on  the  average 
to  1*.  3rf.  per  ton  of  rags  for  soda,  and  about  2s.  for  bleaching-powder.     It 
has,  however,  been  found  more  advantageous  to  forego  this  saving  and  aim 
at  improved  quality  of  pulp  instead. 

3.  Economy  of  water  for  washing  purposes,  1000  gallons  being  sufficient  for  one 
ton  of  rags,  as  against  four  or  five  times  this  amount  by  the  ordinary  process. 

4.  Saving  of  steam  for  heating  and  maintenance  of  steam  pressure.     This  has 
been  found  to  amount  to  about  one-third  of  that  required  by  the  best  system 
of  treatment  in  revolving  boilers,  or  about  Gd.  per  ton  of  rags,  with  coal  at 
15s.  per  ton. 

5.  Improved  strength  of  fibre.     It  has  been  abundantly  proved  in  the  case  of 
cotton  and  linen  textiles  that  a  notable  increase  in  strength  is  obtained  by 
the  use  of  the  kier  as  compared  with  any  other  form  of  boiler.   It  rnay  fairly 
be  assumed,  therefore,  that  the  fibres  suffer  less  damage  from  the  action  of 
the  alkali  in  the  case  of  rags  also. 

6.  An  enormous  saving  in  the  space  occupied.     A  kier  8  feet  long  by  7  feet 
diameter  occupies,  with  turntables,  rails,  etc.,  for  four  extra  wagons,  engine 
for  drivLug  pumps,  etc.,  a  ground  space  of  727  square  feet.     To  this  should 
be  added  the  space  occupied  by  the  overhead  tanks  for  the  caustic  soda, 
making  a  total  of  843  square  feet.   The  ground  space  occupied  by  six  boilers, 
required  to  treat  the  same  amount  of  rags,  would  amount  to  1440  square  feet. 
In  addition  to  this  a  top  floor  of  equal  area  would  be  required  for  filling. 
Together  these  amount   to  2880  square  feet,  as  against  843  square  feet 
required  for  the  kier. 

Treatment  of  Picker  Seed  and  Picker  Waste.  —  These  two 
raw  materials  require  about  the  same  treatment.  They  are  boiled, 
either  in  rotaries  or  open  tubs,  with  rather  weak  lye.  About 
125  Ibs.  of  soda-ash  and  150  Ibs.  of  lime  are  used  to  the  ton  of 
stock.  Treatment  in  the  rotary  requires  about  65  Ibs.  pressure  if 


PROCESSES  FOR  ISOLATING  CELLULOSE. 


157 


the  boiling  is  to  be  completed  in  about  eight  hours.  Twelve  hours 
in  the  open  tub  gives  a  stock  which  bleaches  better  than  that 
obtained  by  boiling  under  pressure.  In  either  case  the  stock  is 
much  improved  by  being  allowed  to  stand  from  six  to  eight  days 
to  soften.  The  same  treatment  applies  to  Cotton  Waste. 

Treatment  of  Esparto.  —  On  account  of  the  high  price  of  this 
material  it  has  never  successfully  come  in  competition  with  poplar 


Fio.  11.  —  VOMITING  BOILER. 

fibre  ti>;  this  country,  but  on  the  Continent,  and  especially  in  Eng- 
land, it  forms  one  of  the  most  important  sources  of  paper-stock. 
The  grass  is  first  picked  over  by  hand  to  remove  root  ends,  weeds, 
etc.,  and  is  then  shaken  and  dusted.  It  is  packed  into  the  boiler 
without  cutting,  as  is  the  case  with  straw.  The  details  of  the 
boiling  operation  vary  much  in  different  mills.  In  a  few  cases 
open  vomiting-tubs  are  used,  but  the  general  practice  is  to  treat, 
under  pressure,  in  vertical  boilers.  In  rotaries  the  fibre  is  likely 


158  TEE  CHEMISTRY  OF  PAPER-MAKING. 

to  roll  up  into  small  balls,  which  make  lumps  in  the  paper.  The 
pressures  carried  vary  from  5  to  50  Ibs.,  and  the  time  of  boil- 
ing is  from  one  and  a  half  to  six  hours.  Caustic-soda  liquor  is 
always  used.  Routledge  gives  10  per  cent,  of  soda  as  the  neces- 
sary amount.  In  one  of  the  best  English  mills  the  practice  is  to 
use  16  Ibs.  of  caustic  per  112  Ibs.  of  grass,  and  to  boil  from 
one  and  a  half  to  two  hours  at  40  Ibs.  pressure. 

One  of  the  best  types  of  boiler  for  esparto  is  shown  in  Fig.  11. 
It  is  a  vomiting-boiler,  the  steam,  which  is  admitted  through  A* 
passing  to  the  bottom  of  the  boiler  before  escaping.  It  then  drives 
upward  through  the  vomit-pipe,  (7,  carrying  with  it  the  liquor 
which  has  worked  below  the  false  bottom,  P,  J?,  and  which  is  then 
discharged  under  the  hood,  D,  which  acts  as  a  spreader.  E  is  the 
manhole  for  filling,  the  manhole  plate  being  secured  by  the  clamps, 
F,  FI  and  balanced  by  the  counterpoise,  L.  The  boiler  is  emptied 
through  H.  K  is  a  safety-valve. 

The  washing  of  the  pulp  and  recovery  of  the  liquors  are  gener- 
ally conducted  as  in  soda-pulp  mills  in  this  country,  but  we  have 
been  in  at  least  one  English  mill  where  no  attempt  at  recovery  was 
made.  In  many  others  the  old-style  pan  evaporators  are  in  use, 
but  they  are  being  replaced  by  the  far  more  economical  multiple- 
effect  Yaryans.  The  ash  in  esparto  is  over  3  per  cent.,  and  consists 
largely  of  silica,  which  forms  silicate  of  soda  in  the  f urnacing  of 
the  liquors,  and  thus  reduces  somewhat  the  per  cent,  of  ash  re- 
covered. A  recovery  of  about  80  per  cent,  is  claimed.  Recent 
experiments  seem  to  show  that  it  is  impossible  to  recover  over  85 
per  cent,  under  the  best  conditions.  The  yield  of  fibre  is  about 
50  per  cent,  and  it  is  bleached  to  good  color  with  7  per  cent,  of 
bleaching-powder. 

Treatment  of  Straw.  —  The  similarity  between  the  plant  sub- 
stance of  straw  and  that  of  esparto  is  sufficiently  close  to  render 
substantially  the  same  methods  of  treatment  applicable  to  both. 
Straw  is,  however,  rather  more  highly  lignified,  and  on  that  ac- 
count requires  the  employment  of  somewhat  higher  pressures, 
or  of  stronger  solutions.  In  the  preliminary  treatment,  the  straw 
is  picked  over  by  hand  to  remove  weeds,  etc.,  and  is  afterwards 
dusted  and  cut  into  small  pieces  one  to  two  inches  long.  Care  is 
taken  to  avoid  the  presence  of  seeds  or  seed  hulls  in  the  material 
ready  for  the  boiler,  as  these  are  reduced  with  difficulty,  and  are 
likely  to  form  specks  in  the  pulp. 


PROCESSES  FOR  ISOLATING   CELLULOSE.  159 


The  different  processes  for  treating  straw  show  considerable 
variation  in  their  details,  according  to  the  kind  and  quality  of 
the  straw  itself,  and  the  purpose  for  which  the  product  is  to  be 
used.  They  nearly  all  show  in  their  general  principles  a  close 
resemblance  to  the  process  of  Mellier,  patented  in  1854,  and  which 
consisted  in  cooking  the  straw,  for  about  three  hours,  at  a  pressure 
of  70  Ibs.,  with  a  solution  of  caustic  soda  contained  in  a  rotary 
digester  heated  by  indirect  steam:  16  Ibs.  of  caustic  were  used 
per  100  of  straw. 

Most  of  the  straw  pulp  made  in  this  country  is  prepared  for  use 
in  strawboard  by  boiling  the  straw  with  lime.  Abroad  the  straw  is 
more  commonly  treated  for  the  production  of  the  pure  fibre.  The 
following  methods  are  among  those  used  in  Germany :  — 

1.  A  charge  of  about  700  kilogrammes  of  straw  is  packed  into  a 
rotating  spherical  digester  of  235  cm.  diameter.     Liquor  is  used 
which  contains  about  13  per  cent,  caustic  soda  figured  on  the  weight 
of  the  straw,  and  the  digester  is  rotated  cold  from  one  to  three 
hours.    The  boiling  is  carried  on  from  six  to  eight  hours,  at  about 
40  Ibs.  pressure. 

2.  A  charge  of  1000  kilogrammes  of  straw  is  extracted  from 
one  to  three  hours  with  warm  water,  which  is  then  drained  off  and 
the  leaching  repeated.     The  mass  is  then  drained  and  packed  into 
a  cylindrical  rotary.    The  lye  is  made  by  dissolving  10  to  14  per 
cent,  caustic-soda,  calculated  on  the  gross  weight  of  the  straw,  in. 
only  enough  v  water  to  well  wet  but  not  to  cover  the  straw.     The 
cooking  is  carried  on  from  four  to  six  hours,  at  a  temperature  of 
about  150°  G.    After  dumping,  the  pulp  is  washed  for  eight  to 
twelve  hours  with  warm  water. 

3.  A  charge   of   1000  kilogrammes  more  or  less  of  straw  is 
packed  and  tamped  into  bags  holding  40  to  60  kilogrammes  each. 
The  bags  are  tied  up  and  packed  in  a  cylindrical  rotary.     The 
cooking  is  carried  on  from  four  to  eight  hours  with  a  caustic  liquor 
standing  5°  to  8°  Be*.      The  pressure  varies  from  75  to  120  Ibs. 
These  variations  in  treatment  are  rendered  necessary  by  the  quality 
of  different  straws  and  the  character  of  pulp  desired. 

4.  In  order  to  obtain  a  strong,  creamy  white  fibre  for  use  in  fine 
writing-papers  the  straw  is  .cut  very  small,  and  carefully  cleaned 
from  all  weeds.     Small  spherical  or  cylindrical  rotaries  are  used. 
The  straw  is  first  cooked  for  five  to  eight  hours,  at  about  60  Ibs. 
pressure,  with  13  to  17  per  cent,  of  lime,  and  sufficient  water  is 


160 


THE  CHEMISTRY  OF  PAPEE-MAKING. 


used  to  keep  the  straw  covered.  It  is  then  dumped  into  washing- 
engines  fitted  with  granite  plates,  and  carefully  washed  and  beaten 
in  order  to  remove  all  the  lime  with  as  little  injury  to  the  fibre  as 
possible.  The  stuff  is  kept  in  drainers  for  about  four  days  in  order 
to  make  it  soft  and  porous,  and  is  then  cooked  for  about  five  hours, 
at  40  Ibs.  pressure,  with  a  soda  lye  containing  6  per  cent,  of  caustic 
soda  on  the  weight  of  the  straw. 

The  mechanical  preparation  of  the  straw  before  cooking  and  the 
treatment  to  which  it  is  afterwards  subjected  have  at  least  as  much 
to  do  with  the  quality  of  the  product  as  the  details  of  the  boiling 
operation. 

Some  manufacturers  find  an  objection  to  the  use  of  rotary  boilers, 
in  the  liability  of  the  short  fibres  to  roll  up  into  little  balls,  which 
are  likely  to  make  spots  in  the  paper.  Partly  on  this  account,  and 
partly  because  of  a  real  or  supposed  economy  of  soda,  vomiting- 
boilers  are  in  use  in  some  mills  abroad,  especially  in  England. 

In  order  to  pack  the  greatest  amount  into  the  rotary  the  digester 
is,  in  some  cases,  filled  with  the  chopped  straw,  and  then  run  for  a 
few  moments  with  a  portion  of  the  liquor,  so  that  the  straw  may 
soften  and  pack  down  sufficiently  to  admit  a  considerable  addi- 
tional quantity.  The  English  practice  in  boiling  shows  the  varia- 
tions noticed  elsewhere,  According  to  Cross  and  Bevan  the  pro- 
portion of  caustic  is  from  10  to  20  per  cent,  of  the  weight  of  the 
straw,  and  the  boiling  is  carried  on  from  four  to  eight  hours,  at 

pressures  ranging  in  the  different 
mills  from  10  to  50  or  even  to 
80  Ibs. 

Glaser,  British  patent  No.  938, 
A.  D.  1880,  subjects  the  straw  pulp 
obtained  by  the  usual  process  of  cook- 
ing to  the  action  of  chlorine  gas,  in 
leaden  or  stone  chambers,  for  several 
hours.  A  very  complete  isolation  of 
the  cellulose  is  thus  secured,  but  the 
pulp  has  afterwards  to  be  bleached 
in  the  ordinary  way  in  order  to  free 


oO 


/-o 


FIG.  12.  — EDOE-RUNXER. 


it  from  all  products  of  the  chlorine  treatment. 

Considerable  rye  straw  is  still  treated  in  France  by  the  following 
method  for  the  manufacture  of  a  coarse  pulp  :  The  straw  is  cut 
quite  short  in  a  cutting-machine.  It  is  then  transferred  into  large, 


THE  MANUFACTURE  OF  WOOD  FIBRE.  161 

rectangular  brick  wells,  and  just  covered  with  dilute  milk  of  lime. 
A  covering  of  heavy  boards  weighted  with  stones  is  put  on,  and 
the  whole  allowed  to  remain  from  two  to  four  weeks.  The  mass 
of  pulp  is  then  removed  and  worked  under  edge-runners  (Fig.  12) 
for  not  less  than  an  hour.  As  the  knots  are  not  softened,  especial 
care  must  be  taken  to  have  the  grinding  well  done.  The  product 
is  harder  than  that  from  straw  which  has  been  treated  in  the  usual 
way. 

On  account  of  the  considerable  proportion  of  silica  present  in 
straw,  it  has  been  generally  assumed  that  this  material  would  not 
easily  lend  itself  to  treatment  by  the  sulphite  process.  Practical 
experience  has,  however,  shown  that  this  is  not  the  case,  and  this 
process  has  recently  been  applied  to  the  preparation  of  straw  pulp 
with  excellent  result. 


THE    MANUFACTURE    OP    WOOD    FIBRE. 

The  Soda  Process.  —  The  efficiency  of  this  process  depends 
partly  upon  the  direct  solvent  and  saponifying  power  of  the  alkali 
at  high  temperatures,  and  partly  ujxm  the  secondary  reactions,  by 
means  of  which  the  acid  products  resulting  from  the  resolution  of 
the  wood  are  brought  into  the  liquor  as  salts  of  soda.  Mere  treat- 
ment in  the  cold  with  dilute  alkali  is  sufficient  to  dissolve  an 
appreciable  portion  of  the  incrusting  matter  of  wood,  and  the  sol- 
vent power  of  the  alkali  is  greatly  enhanced  as  the  temperature 
rises. 

Poplar  is  used  far  more  than  any  other  wood  in  the  soda  proc- 
ess, but  considerable  quantities  of  pine,  spruce,  and  hemlock  are 
consumed  in  making  longer  fibred  stock,  while  such  woods  as 
maple,  cottonwood,  white  birch,  and  basswood  are  not  infrequently 
made  to  replace  poplar.  Maple,  birch,  and  basswood,  however, 
give  so  short  a  fibre  when  used  alone  that  they  are  generally 
mixed  with  poplar. 

On  account  of  the  great  solvent  power  of  the  alkaline  solution, 
comparatively  little  pains  are  necessary  in  the  preparation  of  the 
wood.  The  bark  is  removed,  but  no  attempt  is  made  to  liake  out 
knots  or  portions  which  are  stained  or  rotten.  The  process  reduces 
small  fragments  of  bark  and  knots  to  pulp.  Whole  knots  are 
somewhat  softened,  but  are  easily  removed  by  the  screens.  The 


162  THE  CHEMISTRY  OF  PAPER-MAKING. 

wood  is  always  chipped  in  the  well-known  manner,  and  the  chips 
in  the  best  practice  are  either  sent  through  a  willow  duster  or 
blown  against  a  wire  netting  to  remove  the  dirt  which  collects 
upon  the  piled  wood. 

The  digesters  used  in  this  process  are  all  of  well-known  forms. 
The  most  common  type  is  probably  a  horizontal  cylindrical  rotary, 
about  22  feet  long  by  7  in  diameter,  and  holding  about  three  cords 
of  wood.  Such  digesters  are  usually  heated  by  coils  supplied  with 
steam  through  the  trunnions,  and  revolving  with  the  boiler.  A 
few  spherical  rotaries  are  used,  a  common  size  being  12  feet  in 
diameter,  with  a  capacity  of  about  five  cords.  Many  mills  use 
upright  digesters,  a  few  of  which  are  heated  by  a  steam-jacket,  as 
in  the  Marshall  boiler,  a  few  by  direct  fire,  but  by  far  the  greater 
number  by  live  steam.  It  is  very  difficult  to  keep  an  iron  shell 
tight  in  which  alkaline  solutions  are  boiled,  as  such  solutions  soon 
work  their  way  through  crevices  which  would  be  tight  to  water. 
Leaky  digesters  have  in  the  past  been  a  source  of  much  annoyance 
in  this  process,  but  at  the  present  time  comparatively  little  diffi- 
culty from  this  cause  is  experienced.  The  Marshall  jacketed 
boiler  rested  its  claims  chiefly  upon  the  fact  that  the  pressure  in 
the  jacket  was  always  kept  higher  than  that  in  the  digester,  so  that 
in  case  of  any  leak  in  the  digester  walls  there  was  a  passage  of 
steam  inward  rather  than  a  passage  of  liquor  outward.  A  welded 
digester  is  now  upon  the  market,  which  would  seem  to  make 
further  trouble  from  leakage  unnecessary. 

The  strength  of  liquor  used  varies  from  8°  to  15°  Re*,  at  60°  F., 
according  to  the  pressure  and  time  of  boiling  and  the  manner  in 
which  heat  is  applied  to  the  digester.  Where  heating  is  effected 
by  jackets,  coils,  or  direct  fire,  the  liquor  ordinarily  stands  from 
12°  to  14°  Be*.,  and  contains,  when  properly  causticized,  from  6  to  9 
per  cent,  of  caustic  soda,  NaOH.  With  live  steam  allowance  has 
to  be  made  for  condensed  water,  and  it  is  necessary  to  use  less 
liquor,  but  of  higher  test.  With  indirect  heat  in  rotaries  about 
TOO  gallons  of  liquor  are  used  to  a  cord  of  wood.  Upright  digesters 
require  considerably  more,  or  enough  in  any  case  to  cover  the  wood 
as  soon  as  it  becomes  well  soaked  arid  settles  down. 

As  much  wood  as  possible  is  put  into  the  digester,  arid  in  some 
cases  mechanical  devices  for  tamping  and  packing  the  wood  are 
employed. 

The  boiling  operation  is  a  simple  one.     Full  pressure  is  reached 


THE  MANUFACTURE  OF  WOOD  FIBRE.  163 

as  soon  as  possible,  and  is  maintained  to  the  end  of  the  cook.  Watt 
and  Burgess  are  said  to  have  used  a  lye  of  12°  Be*.,  at  a  pressure  of 
60  Ibs.,  but  the  later  experience  has  been  that  even  75  Ibs.  is  not 
sufficient  to  ensure  a  good  cook,  and  the  tendency  now  is  toward 
the  adoption  of  pressures  above  100  Ibs.  With  90  Ibs.  as  a  mini- 
mum the  present  practice  generally  calls  for  100  to  110  Ibs.  pres- 
sure. The  time  of  boiling  is  eight  to  ten  hours.  As  the  pressure  is 
increased,  the  strength  of  the  liquor  may  be  somewhat  diminished. 
Thus  Koughton,  in  the  early  days  of  the  process,  used  a  lye  of 
4°  Be.,  at  pressures  which  reached  180  Ibs. 

The  practice  necessarily  varies  with  the  character  of  the  wood  to 
be  treated,  and  where  11°  Be*,  gives  good  results  with  poplar,  maple, 
cottonwood,  or  basswood,  a  lye  of  15°  Be",  is  needed  for  spruce, 
pine,  or  hemlock.  The  experiments  of  Tauss  have  shown  that  an 
increase  in  the  time  of  boiling  is  only  a  partial  equivalent  for  the 
use  of  such  stronger  liquors. 

The  pulp  obtained  at  the  close  of  the  cook  is  of  a  grayish  brown 
color,  while  the  liquor  is  a  dark,  rich  brown,  and  has  a  somewhat 
empyreumatic  odor.  It  contains  very  little  alkali  which  is  not  in 
combination  with  the  acid  products  from  the  wood.  The  contents 
of  the  digester  are  dumped  or  blown  into  one  of  a  series  of-  iron 
washing-tanks,  with  drainer  bottoms,  and  the  pulp  is  there  sub- 
jected, after  most  of  the  liquor  has  drained  off,  to  a  thorough  and 
systematic  washing.  It  is  extremely  important  to  remove  the  last 
traces  of  black  liquor  with  as  little  expenditure  of  water  as  possi- 
ble, because  even  a  small  quantity  of  such  liquor  left  in  the  pulp 
renders  bleaching  very  difficult ;  while,  if  a  large  quantity  of  water 
is  used,  the  cost  of  concentrating  the  liquors  in  the  recovery  proc- 
ess becomes  excessive.  For  these  reasons  the  pulp  in  the  different 
tanks  is  washed  with  the  liquor  coming  from  the  tank  before  it  in 
the  series,  and  the  moderate  quantity  of  fresh  water  which  finishes 
the  washing  of  one  lot  of  pulp  passes  in  succession  through  four  or 
five  tanks,  in  each  succeeding  one  of  which  the  quantity  of  black 
liquor  in  the  pulp  is  greater,  until  finally  it  passes  through  the 
pulp  which  has  just  come  from  the  digester,  and  is  brought  up  to 
about  one-half  the  strength  of  the  original  liquor. 

Well- washed  poplar  pulp  made  by  this  process  bleaches  easily 
with  12  to  14  Ibs.  of  bleach  ing-powder  to  the  hundred,  and  then  con- 
sists of  almost  entirely  pure  cellulose.  An  appreciable  portion  of 
the  cellulose  present  in  the  wood  is  dissolved  during  the  boiling, 


164  THE  CHEMISTRY  OF  PAPER-MAKING. 

and  the  yields  are  consequently  lower  in  this  than  in  the  sulphite 
process.  Differences  of  treatment  and  inaccuracies  in  the  measure- 
ment of  wood  make  the  yields  reported  by  the  different  mills  vary 
to  a  considerable  extent,  as  is  shown  by  the  table  on  page  149. 

Unbleached  spruce  pulp  is  soft  and  strong,  but  the  coloring- 
matter  derived  from  the  decomposition  of  the  non-cellulose  por- 
tion of  the  wood  so  nearly  approaches  tar  or  ulmic  compounds  in 
character  that  it  can  only  be  bleached  to  good  color  by  an  oxidizing 
treatment  so  severe  as  to  attack  and  weaken  the  cellulose  itself. 
For  this  reason  most  of  the  spruce  pulp  is  used  in  papers  of  such 
grades  or  tints  that  its  color  is  no  objection. 

Recovery  of  Soda.  —  In  the  early  days  of  the  process  no  attempt 
was  made  to  recover  the  soda  from  the  waste  liquors,  but  the 
nuisance  caused  by  their  discharge  into  running  streams,  and  the 
large  quantity  of  ash  required,  soon  led  to  the  adoption  of  various 
methods  of  reclaiming.  The  character  of  the  waste  liquor  and  the 
combinations  in  which  the  soda  exists  therein  'are  such  as  to  render 
recovery  especially  easy  from  a  chemical  point  of  view.  The  or- 
ganic acids  with  which  the  soda  is  combined,  as  well  as  the  organic 
matter  present  in  other  forms,  represent  nearly  one-half  the  fuel 
value  of  the  original  wood,  and  furnish  by  their  combustion  a 
supply  of  heat  which,  if  utilized  in  a  properly  constructed  appara- 
tus, is  nearly  or  quite  sufficient  to  effect  the  concentration  of  the 
weak  liquors  up  to  the  point  where  they  may  be  ignited.  After 
the  ignition  in  the  presence  of  so  much  carbonaceous  matter,  the 
soda  remains  as  carbonate  in  the  black  ash. 

Among  the  bodies  which  have  been  recognized  in  the  black 
liquor  are  sodium  formate,  oxalate,  and  acetate,  together  with  dark- 
colored  products  similar  to  ulmic  acid.  Sugar  and  bodies  like 
sugar  are  not  present.  According  to  Tauss  the  proportion  of  sub- 
stances which  are  precipitated  by  alcohol  and  acids  becomes 
greater  as  the  pressure  or  the  concentration  of  the  lye  is  in- 
creased. 

Where  the  original  boiling  liquor  was  strong,  and  where  much 
care  is  taken  to  wash  the  pulp  in  a  systematic  manner,  it  is  possi- 
ble to  bring  the  mixture  of  waste  liquor  and  wash  water  up  to  a 
gravity  of  6°  to  9°  Be*,  at  160°  F.  The  higher  gravity  is  very  rarely 
reached,  and  in  some  mills  the  liquors  going  to  the  evaporator  do 
not  stand  over  3°  to  4°  Be",  at  the  same  temperature.  The  follow- 
ing analysis  of  a  partially  concentrated  liquor  indicates  in  a  general 


THE  MANUFACTURE  OF  WOOD  FIBRE.  165 

way  the  proportion  between  the  organic  and  inorganic  constituents 
of  liquors  of  this  class :  — 

Black  liquor  standing  11£°  Be.  at  115°  F. 

Per  cent. 

Water     . 83.51 

Organic  matter 5.96 

Caustic  soda 8.60 

Black  asli  waste  .  1.93 


Tttal    . 100,00 

In  order  to  maintain  a  continuous  combustion  of  the  organic 
matter,  the  liquor  must  be  concentrated  by  evaporation  until  it 
stands  at  least  30°  Be.  at  130"  F.,  and  it  is  desirable  to  bring  up  to 
40°  Be",  or  even  higher. 

In  the  earliest  systems  of  recovery  the  evaporation  was  con- 
ducted in  open  pans,  frequently  arranged  one  above  the  other  to 
avoid  undue  loss  of  heat,  but  the  volume  of  liquor  to  be  concen- 
trated is  so  large  that  such  crude  forms  of  apparatus,  in  which  only 
a  small  proportion  of  the  heating  power  of  the  combustible  is  made 
efficient,  have  now  been  almost  entirely  replaced  by  forms  in  which 
the  principles  of  multiple-effect  evaporation  are  embodied. 

The  boiling-point  of  water  depends,  as  is  well  known,,  upon  the 
pressure  under  which  evaporation  takes  place,  and  is  rapidly 
lowered  as  the  pressure  is  diminished.  Under  the  ordinary  atmos- 
pheric pressure  of  14.7  Ibs.  the  boiling-point  is  212°  F. 

The  lowering  of  the  boiling-point  of  water  by  diminution  of 
pressure  is  shown  by  the  following  table  :  — 

The  temperature  of  water  boiling —  OF> 

at  atmospheric  pressure  is     ....  212 

under    5    ins.  vacuum  is 195 

"     10     «          «            185 

«     15     "          "            160 

"  20  "    «     .....  150 

«  25  «    «     .....  130 

«  26  "    "     .....  120 

"  J27  «    "     .....  112 

"   28  ««    "     .  *  .  .  .  100 

"  29  "    "     .....  72 

«    "     .....  52 


166  THE  CHEMISTRY  OF  PAPER-MAKING. 

Other  liquids  follow  a  similar  rule,  but  have  different  normal 
boiling-points ;  while,  in  case  of  water-holding  substances  in  solu- 
tion, the  boiling  temperature  for  the  different  pressures  is  increased. 

When  water  is  boiled  under  the  ordinary  atmospheric  pressure, 
the  resulting  steam,  like  the  water,  has  a  temperature  of  212°  F., 
and  the  large  quantity  of  heat  necessary  to  con  vert,  the  water  into 
steam  has  been  expended  in  bringing  libout  that  complete  separa- 
tion of  the  molecules  which  constitutes  the  essential  difference 
between  steam  and  water.  That  portion  of  the  heat  which  was 
thus  consumed  or  converted  into  the  energy  of  steam  is  termed 
latent  heat,  and  reappears  when  the  steam  is  condensed.  The  total 


FIG.  13.  —  THE  YARYAX  EVAPORATOR. 

heat  present  in  a  pound  of  steam  at  212°  F.  is  represented  by 
1146.1  thermal  units,  and  of  this  quantity  964.3  thermal  units  are 
in  the  form  of  latent  heat.  This  series  of  facts  is  made  use  of  in 
multiple-effect  evaporation  in  the  following  way:  The  effects,  as 
they  are  called,  are  pieces  of  apparatus  so  arranged  that  the  steam 
or  vapor  from  the  liquid  boiling  in  the  first  effect  can  be  carried 
over  and  used  as  the  heating  agent  in  the  second  effect.  The  boil- 
ing-point of  the  liquid  in  the  second  effect,  and  consequently  the 
temperature  of  the  vapor  issuing  from  it,  is  lowered  by  the  main- 
tenance of  a  partial  vacuum  in  the  second  effect.  The  vapor  from 
this  effect  is  in  the  same  way  used  as  the  heating  agent  in  the  third 
effect,  in  which  the  boiling-point  of  the  liquid  there  present  is  still 
further  reduced  by  the  maintenance  of  a  higher  vacuum.  Three  or 


THE  MANUFACTURE  OF  WOOD  FIBRE. 


167 


four  effects  are  the  number  which  are  ordinarily  used  in  practice, 
but  there  is  in  theory  no  limit  to  the  number  which  mighi  be  used. 
Each  additional  effect  within  practical  limits  increases,  in  a  numer- 
ical ratio,  the  quantity  of  liquor  evaporated  by  given  weight  of 
combustible,  because  in  each  effect  after  the  first  the  vapor  from 
the  preceding  one  is  made  to  give  up  its  latent  heat  to  the  liquor 
in  that  effect. 

Many  different  types  of  multiple-effect  evaporators  have  been 
devised,  but  at  the  present  time  nearly  all  the  work  of  evaporat- 
ing soda  liquors  in  this  way  is  done  by  the  apparatus  known 
as  the  Yaryan  evaporator,  from  its  inventor.  Figure  18  shows 
a  triple-effect  Yaryan  evaporator,  as  ordinarily  designed  for  soda 
liquors,  and  Fig.  14  gives  a  section  through  one  effect.  Each  effect 
consists  of  a  boiler  shell  surrounding  a  number  of  independent 


FIG.  14.  —  THE  YARYAN  EVAPORATOR. 

arranged  in  coils  parallel  with  the  length  of  the  shell.  The 
pipes  are  three  inches  in  diameter,  and  the  liquor  is  admitted  into 
each  coil  through  an  independent  supply  tube  of  relatively  small 
diameter,  and  at  the  back  of  the  apparatus.  The  tubes  in  the  first 
effect  are  heated  by  steam  under  A  pressure  varying  in  different 
mills  from  10  to  45  Ibs.,  and  which  is  admitted  into  the  shell  or 
jacket  which  surrounds  the  coils.  The  small  stream  of  liquor 
entering  at  the  back  end  of  a  coil  is  exposed  to  the  action  of  heat, 
partly  as  a  spray  and  partly  as  a  thin  film  lining  the  interior  of  the 
tube.  Under  the  influence  of  the  partial  vacuum  maintained  in  the 
separating-chamber  in  which  the  coil  ends,  the  liquid  moves  for- 
ward through  the  coil  with  considerable  velocity,  and  is  th  us  con- 
tinually exposing  fresli  particles  to  the  action  of  the  heat.  Five 
lengths  of  pipe  constitute  a  coil,  and  the  liquor,  in  passing  through 
one  effect,  has  therefore  to  travel  a  distance  equal  to  about  five 


168  THE  CHEMISTRY  OF  PAPER-MAKING. 

times  the  length  of  the  shell,  or  60  feet.  The  mixture  of  vapor  and 
liquor  issuing  from  each  of  the  independent  coils  is  discharged  into 
the  separating  head  or  chamber,  which  forms  the  front  of  the  effect, 
and  there  strikes  a  series  of  dash-plates  or  partial  partitions,  the 
openings  through  which  alternate  in  such  a  way  that  the  vapor  and 
liquor  strike  upon  each  plate  in  succession,  and  are  at  last  well 
separated,  the  liquor  falling  into  the  drum  below  the  separator,  and 
the  vapor  passing  over  into  the  shell  or  jacket  of  the  second  effect. 
The  partially  concentrated  liquor  from  the  first  effect  is  delivered 
into  the  coils  of  the  second  effect  through  the  supply  tubes  at  the 
back,  and  on  its  passage  th rough  the  coils  is  heated  by  the  vapor 
given  off  during  its  concentration  in  the  first  effect.  As  the  tem- 
perature of  this  vapor  is  lower  than  that  of  steam  first  used,  the 
boiling-point  of  the  liquor  in  the  second  effect  is  reduced  by  the 
maintenance  of  a  slight  vacuum.  The  liquor  passes  in  succession 
through  each  of  the  effects,  and  the  vapor  from  each  effect  passes 
over  into  the  shell  of  the  next  one,  where  it  is  used  as  the  heating 
agent,  each  effect  being  under  a  higher  vacuum  than  the  one  pre- 
ceding, in  order  to  compensate  for  the  gradual  fall  in  the  tempera- 
ture of  the  vapor.  The  vacuum  is  maintained  by  means  of  a  con- 
denser and  pump ;  while,  by  another  pump,  the  concentrated  liquor 
is  removed  from  the  last  effect.  The  liquor  enters  the  apparatus 
in  a  continuous  stream  at  from  3°  to  8°  Be*.,  and  in  a  few  moments 
has  passed  through  the  entire  system  of  pipes  and  been  discharged 
at  a  density  of  35°  or  more :  42°  Be*,  is  reached  at  times,  but  it  is 
difficult  to  pump  liquor  standing  as  high  as  40°.  The  efficiency  of 
the  Yaryan  is  said  to  be  due  in  part  to  the  much  greater  rapidity 
with  which  liquids  absorb  heat  when  in  motion,  as  compared  with 
the  rate  of  absorption  when  they  are  at  rest.  Jelinck  gives  the 
following  figures  in  this  connection  :  — 

Velocity  of  the  liquid  per  Calories  absorbed  per 

second  in  metres.  square  metre. 

0.312  22.7 

0.640  33.6 

1.020  46.9 

1.640  69.9 

The  Yaryan  evaporator,  in  connection  with  the  Warren  rotary 
furnace,  has  practically  revolutionized  the  recovery  of  soda,  since 
the  expense  is  not  only  greatly  diminished,  but  on  account  of  the 
small  cost  of  evaporation  the  washing  can  be  carried  further  and 


THE  MANUFACTURE  OF   WOOD   FIBRE.  169 

a  considerably  greater  percentage  of  soda  recovered.  Under  the 
best  present  practice  about  2100  gallons  of  liquor  come  to  the 
Yaryan  per  ton  of  pulp  produced,  but  in  some  cases  the  volume 
reaches  3200  gallons  per  ton. 

The  Gaunt  multiple-effect  evaporator,  which  is  a  more  recent 
type  of  apparatus,  has  been  lately  applied  to  the  concentration  of 
soda  liquors.  The  liquor  to  be  evaporated  and  the  heating  agent 
occupy,  in  this  apparatus,  positions  which  are  just  the  reverse  of 
those  in  which  they  stand  to  each  other  in  the  Yaryan ;  that  is,  the 
liquor  flows  by  gravity  over  the  outside  of  the  pipes  in  a  thin 
sheet,  and  the  vapor  from  which  heat  is  derived  is  inside  the  pipe. 
Where  three  or  four  effects  are  used,  they  are  arranged  one  above 
the  other.  The  first  effect  is  the  highest  one,  and  the  liquor  fall- 
ing through  this  collects  in  the  bottom  of  the  effect,  and  flows  into 
the  slotted  liquor-supply  tube  of  the  second  effect,  which  is  im- 
mediately below,  and  so  down  through  the  series  until  it  reaches 
the  bottom  of  the  last  effect,  from  which  it  is  removed  by  pump- 
ing. The  first  effect  is  heated  by  direct  or  exhaust  steam,  which 
is  let  into  the  tubes  under  a  slight  pressure,  and  the  vapor  formed 
as  the  liquor  falls  over  the  tubes  expands  into  the  chamber,  in 
which  they  are  enclosed,  and  passes  over  into  the  tubes  of  the 
second  effect ;  the  vapor  from  this  effect  passes  into  the  tubes  of  the 
one  following,  and  so  on.  The  amount  of  vacuum  maintained  on 
each  effect  is  regulated  by  the  height  of  the  liquid  seal  formed  by 
the  liquor  in  the  bottom  of  each  effect.  The  vapor  from  the  last 
effect  passes  over  to  the  condenser,  which  maintains  the  vacuum. 

Partly  on  account  of  the  thick  and  tarry  nature  of  the  highly 
concentrated  liquors,  which  retards  theif  motion  through  an 
evaporator  and  makes  pumping  difficult,  and  partly  because  of 
the  tenacity  with  which  the  last  portions  of  water  are  held  by  the 
dissolved  substances,  the  evaporation  of  such  liquors  cannot  be 
economically  carried  above  40°  Be*.  The  amount  of  water  still 
present  is  too  great  for  the  liquors  to  maintain  their  own  com- 
bustion, but  when  run  into  a  furnace,  through  which  the  flames 
from  a  fire-box  pass,  they  soon  take  fire  and  greatly  increase  the 
amount  of  heat  which  would  otherwise  pass  from  the  furnace. 
The  earliest  style  of  black-ash  furnace  consisted  of  a  pan,  over 
which  the  flames  from  the  fire-box  passed  as  in  the  reverberatory 
furnaces  used  in  the  soda  manufacture.  Such  furnaces  are  still 
used  in  a  few  mills,  and  have  openings  at  intervals  along  the  sides, 


170  THE  CHEMISTRY  OF  PAPER-MAKING. 

through  which  the  workman,  by  means  of  a  long  rake,  gradually 
moves  the  burning  material  from  the  back  towards  the  front  of  the 
pan,  at  which  point  it  is  withdrawn  after  the  ignition  is  complete. 
In  this  country  such  furnaces  have  been  almost  entirely  superseded 
by  the  Warren  rotary  furnace,  which  is  shown,  with  its  auxiliary 
apparatus,  in  Fig.  15.  In  the  drawing,  A  is  the  movable  fire-box, 
built  of  fire-brick,  either  inside  an  iron  shell  or  held  together  by 
iron  rods  and  bands.  It  is  mounted  on  wheels  resting  upon  rails, 
so  that  it  may  be  easily  moved  away  to  give  access  to  the  furnace. 
It  is  either  fitted  with  grate  bars  for  burning  coal  or  wood,  or  may 
be  arranged  for  gas  or  oil. 

The  furnace  itself,  6r,  consists  of  an  iron  shell  lined  with  fire- 
brick in  such  a  way  that  the  interior  is  conical,  the  larger  end 
of  the  cone  being  toward  the  fire-box.  The  furnace  is  encircled  by 
iron  rails,  which  Test  upon  flanged  wheels,  as  shown  at  L,  and  is 
made  to  revolve  by  the  worm  and  gear  and  gear  and  pinion  shown 
•at  M.  The  concentrated  liquor  is  admitted  to  the  furnace  in  a 
regulated  stream  at  J",  and  gradually  works  its  way  forward,  being 
exposed  to  more  and  more  intense  heat,  until  practically  all  the 
organic  matter  has  been  destroyed,  and  the  ignited  black  ash  falls 
out  at  J\Tinto  an  iron  cart  or  conveyer.  In  order  to  utilize  the  waste 
heat  from  the  furnace,  a  boiler,  0,  is  set  up  in  such  relation  to  it 
that  the  hot  gases  pass  under  the  boiler  and  then  through  the 
tubes.  By  this  arrangement  a  quantity  of  steam  may  be  generated 
nearly  sufficient  to  carry  on  the  whole  process  of  evaporation  up 
to  the  point  where  the  liquors  enter  the  furnace.  A  considerable 
proportion  of  the  heat  still  remaining  in  the  gases  is  taken  up 
by  the  concentrated  liquor  in  the  tank,  H,  mounted  over  the 
boiler. 

The  throat  of  the  furnace  is  protected  by  the  water-jacket,  A", 
fastened  to  the  back  of  the  fire-box,  and  projecting  a  short  distance 
into  the  furnace.  This  jacket  is  filled  with  concentrated  liquor 
from  the  tank  H.  The  colder,  and  therefore  heavier,  liquor  flows 
in  at  the  bottom  of  the  jacket,  through  the  pipe  F,  and  being  ex- 
panded by  the  heat  becomes  lighter,  and  is  forced  back  into  the 
tank  through  the  pipe  .Z7,  as  fresh  portions  of  the  colder  liquor  pass 
down  F.  In  this  way  a  constant  oireu!at ion  and  rapid  heating  of 
the  liquor  in  the  tank  are  secured.  Those  portions  of  the  pipes,  E 
and  F,  which  are  fastened  to  the  jacket  are  of  smaller  diameter 
than  the  portions  coming  from  the  tank,  and  project  into  them 


THE  MANUFACTURE  OF   WOOD  FIBRE. 


171 


172 


THE  CHEMISTRY  OF  PAPER-MAKING. 


through  stuffing-boxes,  so  that  the  fire-box  may  be  moved  back 
without  breaking  the  connection. 

We  are  indebted  to  Cross  and  Be  van's  "  Paper-making  "  for  the 
following  cuts  and  description  of  the  Porion  evaporator,  which  is 
one  of  the  most  economical  of  the  large  class  of  evaporators  in 
which  the  liquors  are  not  treated  in  multiple  effect.  It  is  shown 
in  sectional  elevation  and  plan  in  Figs.  16  and  17.  It  is  largely 


FIG.  1C.  —  THE  Pomox  EVAPORATOR — SECTION. 

used  on  the  Continent  and  also  in  England  and  Scotland.  It  con- 
sists of  a  large  chamber,  &,  the  floor  of  which  is  slightly  inclined 
from  the  chimney  shaft,  and  through  which  the  waste  heat  from 
the  furnace,  a,  passes. 

The  liquor  to  be  evaporated  is  run  in  at  the  end  nearest  the 
chimney  from  the  tank  placed  above  the  chamber,  c.  A  number  of 
cast-iron  fanners,  i,  dip  into  the  liquor  and  revolve  rapidly,  usually 


FIG.  17- — THE  PORIOX  EVAPORATOR  — 

at  the  rate  of  about  300  revolutions  per  minute,  producing  and 
filling  the  chamber  with  a  very  fine  spray,  thus  presenting  a  very 
large  evaporating  surface. 

Between  the  furnace  and  the  evaporator  are  placed  the  chambers 
c  and  /.  In  c  a  number  of  brick  walls,  d,  are  so  placed  that  the 
flames  from  the  furnace  are  intercepted  and  broken  up.  The  object 
of  this  is  to  give  time  for  all  the  products  of  combustion  to  be 
thoroughly  burned  up,  which  would  not  be  the  case  without  the 
"  small  consumer,"  as  these  chambers  are  called.  This  part  is  an 


THE  MANUFACTURE  OF  WOOD  FIBRE.  173 

addition  to  the  original  evaporator,  and  was  devised  by  Messrs. 
Menzies  and  Davis.  The  liquor,  after  having  been  concentrated 
in  the  chamber,  k,  runs  into  a  trough  placed  alongside  the  doors,  A, 
and  flows  into  one  or  the  ether  of  the  furnace  beds,  #,  where  it  is 
still  further  concentrated,  and  the  residue  ignited  by  the  flames 
from  the  fires  at  a.  The  draught  can  be  regulated  by  the  damper,  </, 
and  also  by  one  placed  near  the  shaft,  /.  The  doors,  e,  in  the 
smell-consuming  chamber  are  for  the  purpose  of  cleaning  out.  The 
fanners,  i>  are  worked  by  a  small  steam-engine  not  shown  in  the 
drawing.  The  temperature  of  the  gases  near  the  chimney  should 
not  be  higher  than  about  85°  C.  By  running  the  fanners  at  a  veiy 
high  speed  the  temperature  of  the  gases  may  be  still  further 
reduced,  thus  showing  the  completeness  of  the  evaporation. 

This  form  of  evaporator  is  open  to  the  objection  that  the  whole 
of  the  sulphur  in  the  coal  employed  for  the  furnaces  finds  its  way 
into  the  recovered  soda.  It  combines  with  the  alkali  to  form 
sulphite  of  soda,  part  of  which  is  decomposed  in  the  furnace  with 
formation  of  sodium  sulphate,  sulphide,  and  other  sulphur  com- 
pounds. The  same  objection,  of  course,  applies,  though  perhaps  in 
a  less  degree,  to  all  systems  of  evaporation  in  which  the  flame  is  in 
contact  with  the  liquors  to  be  evaporated. 

The  Porion  evaporator  can  be  erected  at  very  small  cost,  and 
costs  but  little  for  maintenance.  It  is  capable  of  producing  three- 
quarters  of  a  ton  of  recovered  soda  per  ton  of  coal  with  liquors  of 
the  usual  strength. 

A  profitable  outlet  for  black-ash  waste  has  recently  been  opened 
up  by  a  process  for  its  conversion  into  carbons  for  arc  lights. 

Causticizing.  —  The  strong  solution  of  carbonate  of  soda  pre- 
pared from  the  mixture  of  black  ash  and  fresh  soda-ash  is  made 
caustic  by  treatment  with  lime  in  tanks,  about  10  feet  in  diameter 
by  7  feet  in  height,  fitted  with  agitators  and  usually  with  drainer 
bottoms.  For  every  100  Ibs.  of  carbonate  of  soda  in  the  liquor 
about  60  Ibs.  of  lime  are  either  thrown  directly  into  the  tank  or 
else  immersed  in  the  liquor  in  an  iron  cage  fastened  to  the  side  of 
the  tank.  The  lime  soon  slakes,  and  is  earned  into  the  liquor, 
which  takes  on  the  appearance  of  milk  of  lime.  The  small  quantity 
of  lime,  which  at  first  goes  into  solution,  reacts  with  the  carbonate 
as  shown  below  — 

CaH202  +  NaaCOs  =  CaC03  -f-  2  NaOH, 


174  THE  CHEMISTRY  OF  PAPER-MAKING. 

and  is  precipitated  as  carbonate  of  lime  ;  an.  equivalent  portion  of 
fresh  lime  is  immediately  dissolved,  and  the  reaction  continues 
until  either  the  lime  is  exhausted  or  all  the  soda  causticized.  In 
order  to  hasten  the  reaction  the  mixture  is  usually  heated  to  about 
212°  F.  by  a  steam-pipe  passing  through  the  bottom  of  the  tank. 

The  character  of  the  lime  used  in  causticizing  is  of  the  first 
importance  if  good  results  are  to  be  secured.  It  should  contain  as 
little  silica  as  possible,  since  otherwise  there  will  be  a  loss  through 
the  formation  of  silicate  of  soda,  and  the  proportion  of  magnesia 
should  be  small  because  of  the  great  insolubility  of  this  base,  which 
renders  it  comparatively  ineffective. 

We  give  below  analyses  of  two  samples  of  lime,  the  sample 
marked  No.  I.  being  especially  good  for  causticizing,  while  that 
marked  No.  II.  is  not  at  all  well  suited  for  the  purpose :  — 

No.  I.  No.  II. 

Sand  and  insoluble  material    .     .  0.08  3.16 

Iron  and  alumina  oxides      .     .     .  0.89  2.67 

Lime 94.07  54.04 

Magnesia.     ........  1.20  36.80 

Water,  carbonic  acid,  etc.    .     .     .  3.7G  3.33 

Totals 100.00          100.00 

Solvay,  in  his  British  patent  of  1879,  claims  that  lime  slaked  in 
a  solution  of  calcium  chloride  gives  a  granular  hydrate  which 
thoroughly  causticizes  the  hot  liquors,  which  are  merely  run  over  a 
layer  of  the  material.  The  hydrate  does  not  lose  its  form,  and  can 
therefore  be  very  easily  and  thoroughly  washed. 

G.  Lunge  has  obtained  the  following  results  from  experiments 
to  determine  how  completely  sodium  carbonate  may  be  converted 
into  caustic  soda  by  treatment  with  lime.  At  the  ordinary  atmos- 
pheric pressure  the  experiments  gave  the  following  numbers :  — 


Per  cent.  Na,CO3  Specific  gravity  before      ,  by  treatment, 

caufiticizing. 


Percentage  of  soda  made  caustic 

by  treatment, 
in  liquor.  caufiticizing.  I.  II. 

2  1.022  at  15°  C.  99.4  99.3 

5  1.052        "  99.0  99.2 

10  1.107         "  97.2  97.4 

12  1.127        «  96.8  96.2 

14  1.150         «  94.5  95.4 

16  1.169  at  30°  C.  93.7  94.0 

20  1.215        «  90.7  91.0 


THE  MANUFACTURE  OF   WOOD  FIBRE.  175 

Corresponding  experiments,  conducted  under  pressure,  at  a.  tem- 
perature of  148°  to  153°  C.,  gave  — 

Percentage  of  soda  made  caustic 

Fer  cent.  Xa,CO3  Specific  gravity  before  by  treatment. 

in  liquor.  causticizing.  I.  II. 

10  1.107  at  15°  C.  97.06  97.50 

12  1.127         "  96.35  96.80 

14  1.150        "  95.60  96.60 

16  1.169  at  30°  C.  95.40  94.80 

20  1.215        «  91.66  91.61 

From  which  it  appears  that  there  is  no  appreciable  gain  when  the 
operation  is  performed  under  pressure,  and  that,  as  was  already 
held,  the  best  results  are  obtained  from  the  weaker  liquors. 

Mills  which  are  located  upon  small  streams  sometimes  experi- 
ence considerable  difficulty  in  disposing  of  the  waste-lime  mud 
from  the  causticizing  tanks.  This  difficulty  has  been,  met  by  the 
lime  reclaimer  invented  by  Mr.  George  W.  Hammond,  and  shown 
in  section  in  Fig.  18.  The  lime-mud  is  fed  at  G  into  the  flue,  F, 
which  is  24  feet  long,  and  through  which  the  mud  is  slowly 
carried  forward  by  means  of  an  Archimedes  screw.  The  nearly 
dry  mud  is  then  discharged  into  the  rotary  furnace,  <7,  which 
is  driven  by  gears  as  shown  at  H.  The  material  coming 
from  this  furnace  is  guided  by  the  connecting  flue,  D,  into  the 
second  furnace,  C\  which  discharges  the  recovered  lime  through 
the  opening  B,  in  front  of  the  fire-box,  A.  In  order  to  drive  off 
all  the  water  and  set  free  the  carbonic  aeid,  a  very  high  tempera- 
ture and  a  considerable  period  of  time  are  necessary,  so  that  very 
long  furnaces  are  required  if  the  process  is  to  be  continuous  and 
the  output  at  all  large.  In  the  apparatus  erected  by  Mr.  Ham- 
mond each  furnace  is  40  feet  longv  and  the  capacity  is  about  ftve 
tons  of  recovered  lime  per  day* 

The  Hewitt  and  Mond  eaustieiziny  process,  or  the  ferric  oxide 
process,  as  it  is  called,  has  been  lately  introduced  in  England,  and 
depends  upon  the  fact  that  when  a  mixture  of  ferric  oxide  and 
carbonate  of  soda  is  strongly  ignited  tlw  iron  acts  as  an  acid  to 
displace  the  carbonic  acid  with  the  formation  of  sodium  ferrate 
which  is  so  unstable  that  washing  with  hot  water  removes  the 
caustic  soda,  leaving  the  ferric  oxide  in  condition  to  be  used  again. 
In  practice,  three  parts  of  ferric  oxide,  originally  in  the  form  of 
"  Blue  Billy,"  which  is  the  cinder  from  pyrites  burning,  are  used 
to  every  one  part  of  soda-ash. 


176 


THE  CHEMISTRY  OF  PAPER-MAKING. 


THE  MANUFACTURE  OF  WOOD  FIBRE.  177 

An  analysis  by  ourselves  of  the  "Blue  Billy"  as  used  gave 
figures  as  below  :  — 

Per  cent. 

Moisture  (loss  on  ignition) 7.50 

Sesquioxide  of  iron  (Fe2O3) 65.49 

Alumina  (A1203)     , 0.89 

Sand  and  silica  (insoluble  in  acid)    ....  24.72 

Oxides  of  lead  and  copper    .......  traces. 

A  rotary  furnace,  usually  18  feet  long  and  10  feet  in  diameter, 
is  charged  with  two  tons  of  the  mixture  of  this  material  and  soda- 
ash,  and  turned  at  the  rate  of  one  and  a  quarter  revolutions  per 
minute  in  order  to  prevent  fluxing.  About  1400°  F.  seems  to  be 
the  temperature  necessary  for  the  reaction,  and  most  of  the  time 
is  consumed  in  bringing  the  charge  to  that  heat.  The  reaction 
proceeds  rapidly  after  it  is  once  begun.  About  five  charges  can  be 
worked  in  such  a  furnace  in  twenty-four  hours,  with  the  consump- 
tion of  seven  long  tons  of  coal.  The  ferrate  of  soda  is  removed  to 
tanks  fitted  with  drainer  bottoms,  and  is  there  leached  with  hot 
water  in  the  same  systematic  way  in  which  black  ash  is  treated. 
In  order  to  settle  out  all  of  the  oxide  of  iron  it  is  necessary  to 
allow  the  liquors  to  stand  about  four  days.  It  is  possible  by  this 
process  to  make  liquors  of  a  strength  of  80°  T. 

The  percentage  of  soda  recovered  varies,  of  course,  within  con- 
siderable limits,  according  to  the  efficiency  of  the  apparatus  and 
the  care  with  which  the  different  stages  of  the  process  are  con- 
trolled. Some  mills  fail  to  recover  more  than  60  per  cent.,  while 
others,  in  exceptional  months,  show  figures  as  high  as  95  per  cent. 
The  average  recovery  is  probably  from  75  to  78  per  cent.,  but  in 
the  best  practice  the  amount  reclaimed  runs  from  85  to  90  per  cent. 
The  percentage  of  recovery  at  the  Willsborough  Mill  of  the  New 
York  and  Pennsylvania  Company  for  1891  is  given  to  us  as  89.11 
per  cent. 

The  main  sources  of  loss  in  recovery  are  :  — 

Imperfect  washing  of  the  pulp. 

Volatilization  of  the  carbonate  in  the  furnace,  or,  which  amounts 

to  the  same  thing,  its  escape  as  dust  carried  into  the  chimney 

mechanically  by  the  furnace  gases. 
Imperfect  leaching  of  the  black  ash. 
Retention  of  soda  in  the  lime-mud  after  causticizing. 


178  THE  CHEMISTRY  OF  PAPER-MAKING. 

The  greatest  loss  is  likely  to  occur  in  washing  the  pulp,  and 
this  can  only  be  kept  down  by  conducting  the  operation  in  the 
most  systematic  and  thorough  manner  possible.  With  great  care 
the  losses  in  causticizing  and  in  leaching  the  black  ash  need  not 
amount  together  to  more  than  1  per  cent.  An  appreciable  quan- 
tity of  soda  is  undoubtedly  lost  up  the  chimney,  and  it  is  difficult 
to  either  check  this  loss  or  accurately  estimate  its  amount.  This 
item  is  a  sort  of  residuary  legatee,  to  which  is  credited  the  balance 
of  loss  which  cannot  properly  be  charged  to  the  other  accounts.  In 
running  a  soda  pulp  mill  the  most  careful  superintendence  is  likely 
to  be  thwarted  unless  it  is  supplemented  by  careful  and  frequent 
chemical  tests  at  every  stage  of  the  process.  Such  tests  are  fully 
described  in  the  chapter  on  Chemical  Analysis. 

The  following  figures,  which  are  taken  from  mill  records,  are  of 
interest  as  showing  the  minimum  to  which  the  losses  at  the  points 
indicated  have  been  brought  in  practice  :  — 

In  washing  .........         2  to  3  per  cent. 

Causticizing  and  leaching  black 

ash,  together 0.75  to  1       " 

Up  chimney 2  to  3       " 

The  Sulphate  Process.  —  This  interesting  modification  of  the 
soda  process  was  introduced  by  Dahl,  at  Danzig,  about  1883.  In 
it  sulphate  of  soda  is  made  to  replace,  in  large  part,  the  more 
expensive  carbonate.  According  to  Schubert,  the  liquor  is  in  the 
first  instance  made  up  from  a  mixture  of  three  parts  sulphate  of 
soda  and  one  part  caustic.  After  cooking  the  wood,  the  liquor  is 
evaporated  and  calcined,  and  yields  a  reddish  brown  ash,  which  has 
about  this  composition  :  — 

Per  cent. 

Sodium  sulphate 16 

"  carbonate .50 

"  hydrate 20 

"  sulphide  . 10 

Various  materials 4 

ioo 

The  composition  of  the  ash  varies,  however,  according  to  the 
treatment,  but  the  solvent  power  of  the  liquor  made  therefrom  is 
not  especially  affected.  The  loss  in  recovery  is  10  to  20  per  cent. 
New  liquor  is  then  made  by  adding  sufficient  sulphate  of  soda  to 


THE  SULPHITE  PROCESS.  179 

replace  the  salts  lost,  and  heating  the  whole  with  20  to  25  per 
cent,  of  lime.  In  regular  operation  the  boiling  liquors  generally 
contain  a  mixture  of  salts  composed  of  about  — 

37  parts  sodium  sulphate. 

8  parts  sodium  carbonate. 
24  parts  sodium  hydrate. 

3  parts  sodium  sulphide. 

The  strength  of  the  lyes  ranges  from  6  to  14°  Be*.  Iron  boilers 
are  used,  and  the  cooking,  which  requires  from  thirty  to  forty 
hours,  is  conducted  at  a  pressure  of  75  to  150  Ibs.  The  main  objec- 
tion to  the  process  is  found  in  the  stench  which  necessarily  arises 
from  the  sulphides  present  in  the  liquors.  Sulphate  pulp  is  of 
excellent  quality,  soft  and  strong.  That  found  in  this  market  is 
made  from  coniferous  trees,  probably  spruce  and  fir.  Three  grades 
are  common  —  the  unbleached,  half-bleached,  and  bleached. 


THE   SULPHITE   PROCESS. 

The  first  patent  involving  the  use  of  sulphurous  acid  in  reducing 
wood  to  pulp  was  that  numbered  70,485,  and  issued  Nov.  5,  1867, 
to  Benjamin  C.  Tilghman,  then  of  Philadelphia,  and  a  chemist  to 
whom  many  branches  of  technology  are  much  indebted.  A  sup- 
plementary patent,  Number  92,229,  covering  the  treatment  of 
fibrous  materials  at  the  ordinary  pressure,  was  issued  to  the  same 
inventor  in  1809.  These  patents  form  the  basis  of  all  the  various 
modifications  of  the  process  in  operation  at  the  present  time. 
The  numerous  subsequent  patents  to  other  inventors  cover  merely 
improvements  in  apparatus  and  details  of  treatment. 

Tilgliman  states  that  his  invention  consists  in  a  process  of  treat- 
ing vegetable  substances  which  contain  fibres  with  a  solution  of 
sulphurous  acid  in  water,  heated  in  a  close  vessel,  under  a  pressure 
sufficient  to  retain  the  acid  gas  until  the  intercellular  incrusting 
or  cementing  matter  existing  between  the  fibres  is  dissolved,  either, 
partially  or  wholly,  as  may  be  desired,  and  a  fibrous  product  is 
obtained  suitable  for  the  manufacture  of  paper  pulp  or  of  fibres,  oj; 
for  other  uses,  according  to  the  nature  of  the  material  employed.  '  v 

The  following  abstract  of  Tilghman's  original  patent  will  serve 
to  indicate  how  carefully  and  thoroughly  he  had  worked  hk 


180  THE  CHEMISTRY  OF  PAPER-MAKING. 

process  out  in  the  experimental  way,  and  how  clearly  he  perceived 
all  its  possibilities.  His  difficulties,  which  he  later  found  too  seri- 
ous for  him  to  overcome,  were  evidently  confined  almost  entirely 
to  the  engineering  side  of  the  process. 

The  specification  calls  for  a  strong  iron  vessel  of  convenient 
size  and  shape,  lined  with  lead,  and  provided  with  a  steam  jacket, 
and  with  the  necessary  pipes,  cocks,  and  manholes  for  filling  arid 
emptying  the  charge;  and  with  gauges,  safety  valves,  and  ther- 
mometers to  indicate  height  of  liquid,  pressure,  and  temperature. 
This  vessel  is  about  two-thirds  filled  with  chips,  hemlock  or  poplar 
being  specified.  A  solution  of  sulphurous  acid  in  water,  of  specific 
gravity  1.025  to  1.035,  in  which  a  quantity  of  sulphite  of  lime 
lias  been  dissolved,  sufficient  to  raise  its  density  to  about  1,07  to 
1.08,  is  run  in  until  the  amount  is  sufficient  to  keep  the  wood 
constantly  covered  by  the  liquid  during  treatment.  The  boiling 
is  conducted  for  about  eight  hours,  at  260°  F.,  when  fresh  water  is 
forced  in  at  the  top  of  the  digester  to  wash  out  the  acid  solution. 
If  the  pulp,  upon  examination,  proved,  as  was  undoubtedly  the 
case,  to  be  imperfectly  separated,  it  was  to  be  again  treated  with 
a  fresh  charge  of  sulphurous  acid  and  sulphite  at  a  temperature 
from. 260  to  280°  F.,  for  three  to  five  hours,  as  might  be  necessary. 
The  patentee  speaks  of  the  quantity  of  sulphite  of  lime  deposited 
during  the  boiling,  and  points  out  that  it  may  be  re-used  together 
with  the  sulphurous  acid  gas  which  may  be  driven  off  from  the 
waste,  liquor.  He  states  that  the  stronger  the  acid  solution,  the 
more  rapid  is  the  action  at  a  given  temperature.  Also,  the  higher 
the  temperature,  the  more  rapid  is  the  action  with  a  given  density 
of  solution ;  with  weak  acid  and  comparatively  low  temperature, 
he  says,  foreshadowing  the  Mitscherlich  process,  the  effect  can 
be  produced  by  continuing  the  digestion  a  sufficiently  long  time. 
Sulphurous  acid  in  water  at  the  requisite  temperature  appears  to 
be  the  efficient  agent  in  dissolving  the  intercellular  or  cementing 
matter  of  the  vegetable  fibrous  substance,  and  where  the  color  of 
the  product  is  of  no  consequence,  the  operation  may  be  performed 
with  the-  sulphurous  acid  alone,  without  the  addition  of  sulphite. 
In  this  case  a  reddish  brown  color  is  given  to  the  resulting  fibrous 
product,  and  the  acid  solution  will  be  found  to  contain  a  quantity 
of  free  sulphuric  acid,  which  has  been  formed  during  the  operation 
by  the  oxidation  of  a  portion  of  the  sulphurous  acid.  This  is 
directly  in  line  with  the  Pictet  process.  The  presence  of  a  sul- 


THE  SULPHITE  PROCESS.  181 

phite  in  the  acid  solution  prevents  this  reddening  effect,  and  in 
case  of  maiiy  substances  a  considerable  bleaching  of  the  fibrous 
product  takes  place. 

Tilghman's  idea  at  this  time  was  that  the  office  of  the  sulphite 
was  to  present  a  base  with  which  the  sulphuric  acid  could  combine 
as  fast  as  formed,  and  he  therefore  naturally  supposed  that  many 
other  of  the  salts  of  the  weaker  acids,  such,  for  example,  as  the 
acetates,  could  replace  the  sulphites  more  or  less  perfectly,  in 
the  presence  of  sulphurous  acid.  Subsequent  experiments  and  a 
more  complete  knowledge  of  the  chemical  process  have  shown 
this  to  be  incorrect,  since  the  sulphite  not  only  neutralizes  the 
free  sulphuric  acid,  but  has  also  a  very  important  influence  in 
the  process  depending  upon  its  power  of  forming  double  com- 
pounds with  certain  of  the  derivatives  of  the  wood. 

On  account  of  their  historical  interest  and  important  bearing  on 
the  process,  we  give  below  in  full  the  claims  of  Tilghman's  first 
patent :  — r 

The  process  of  treating  vegetable  substances  which  contain  fibres  with  a 
solution  of  sulphurous  acid  in  water,  either  with  or  without  the  addition  of 
sulphites  or  other  salts  of  equivalent  chemical  properties  as  above  explained, 
heated  in  a  close  vessel,  under  pressure,  to  a  temperature  sufficient  to  cause  it  to 
dissolve  the  intercellular  incrusting  or  cementing  constituents  of  said  vegetable 
substances,  so  as  to  leave  the  undissolved  produce  in  a  fibrous  state,  suitable  for 
the  manufacture  of  paper,  paper-pulp,  cellulose,  or  fibres,  or  for  other  purposes, 
according  to  the  nature  of  the  material  employed. 

I  also  claim  as  new  articles  of  manufacture  the  two  products  obtained  by 
treating  vegetable  substances  which  contain  fibres  with  a  solution  of  sulphurous 
acid  in  water*  either  with  or  without  the  addition  of  sulphites  or  other  salts 
of  4*qiHvalent  chemical  properties  as  above  explained,  heated  in  a  close  vessel, 
under  pressure,  to  a  temperature  sufficient  to  cause  it  to  dissolve  the  intercellular 
or  incrusting  constituents  of  said  vegetable  substances,  one  of  said  products 
being  soluble  in  water,  and  containing  the  elements  of  the  starchy,  gummy,  and 
saline  constituents  of  the  plants,  and  the  other  product  bekig  an  insoluble 
fibrous  material,  applicable  to  the  manufacture  of  paper,  cellulose,  or  fibres,  or 
to  other  purposes,  according  to  the  nature  of  the  material  employed. 

I  also  claim  the  use  and  application,  in  the  manufacture  of  paper,  paper-pulp, 
cellulose,  and  fibres,  of  the  fibrous  material  produced  by  treating  vegetable 
substances  which  contain  fibres  with  a  solution  of  sulphurous  acid  in  water, 
either  with  or  without  the  addition  of  sulphites  or  other  salts  of  equivalent 
chemical  properties  as  above  explained,  heated  in  a  close  vessel,  under  pressure, 
to  a  temperature  sufficient  to  cause  it  to  dissolve  -the  incrusting  or  intercellular 
constituents  of  said  vegetable  substances. 

I  also  claim  the  use  and  application  of  sulphites  or  other  salts  of  equivalent 


182  THE  CHEMISTRY  OF  PAPER-MAKING. 

chemical  properties  as  above  explained,  in  combination  with  a  solution  of 
sulphurous  acid  in  water,  as  an  agent  in  treating  vegetable  substances  which 
contain  fibres,  when  heated  therewith  in  a  close  vessel,  under  pressure,  to  a 
temperature  sufficient  to  cause  said  acid  solution  to  dissolve  the  intercellular  or 
incrusting  constituents  of  said  vegetable  substances. 

T  also  claim  the  recovery  and  re-use  of  sulphurous  acid  and  sulphite  from  the 
acid  liquids  which  have  been  digested  on  the  vegetable  fibrous  substances,  by 
boiling  said  liquids  or  neutralizing  them  with  hydrate  of  lime. 

Theory  of  the  Sulphite  Process.  —  It  is  well  known  that 
many  of  the  more  complex  members  of  the  carbohydrate  group,  to 
which  cellulose  belongs,  undergo  more  or  less  pronounced  change 
upon  being  boiled  with  water,  especially  if  the  boiling  is  conducted 
at  the  higher  temperatures  obtained  under  pressure  in  a  closed 
vessel.  Sugar,  which  is  the  typical  member  of  the  group,  becomes 
inverted  ;  that  is,  the  sugar  combines  to  a  limited  extent  with  the 
elements  of  water,  and  the  more  complex  molecule  thus  formed 
breaks  down  into  the  two  simpler  ones  of  dextrose  and  levulose. 
Such  an  action  in  which,  as  a  result  of  taking  up  the  elements  of 
water,  a  molecule  is  broken  down,  is  called  a  hydrolytic  action,  and 
the  decomposition  itself  is  called  hydrolysis.  Similar  changes,  as 
before  stated,  are  brought  about  through  the  action  of  water  alone 
upon  the  more  complex  carbohydrates,  such  as  cellulose  and  its 
incrusting  matters,  if  not  upon  all  the  members  of  the  group ;  but 
these  changes  proceed  far  more  rapidly  and  completely  in  the 
presence  of  dilute  acids.  Cellulose  itself  is  comparatively  stable 
under  these  conditions,  unless  the  temperature  is  considerably 
raised,  but  Tauss  and  others  have  shown  that  it  is  by  no  means  un- 
acted upon.  Lignin,  probably  from  its  greater  complexity,  is  broken 
down  with  considerable  rapidity  at  temperatures  not  much  higher 
than  that  of  the  boiling-point  of  water.  The  products  of  the  decom- 
position are  largely  organic  acids,  and  the  direction  of  the  decom- 
position is  toward  the  production  of  these  acids,  but  among  the 
earlier  products  there  undoubtedly  occur  a  considerable  proportion 
of  substances  having,  jgb  least,  the  general  character  of  the  alde- 
hydes. When  the  ordinary  mineral  acids,  as  sulphuric  or  hydro- 
chloric acid,  act  in  the  dilute  form,  and  at  moderately  high  tempera- 
tures, upon  wood,  the  decomposition  products  rapidly  accumulate 
in  the  liquor,  and  undergo  further  secondary  decompositions,  the 
course  of  which  tends  toward  the  production  of  insoluble,  dark- 
colored,  and  tarry  matters.  It  is  obviously  impossible  under  these 


THE  SULPHITE  PROCESS.  183 

conditions  to  look  for  the  production  of  cellulose  in  any  condition 
of  purity. 

The  reaction  undoubtedly  takes  a  somewhat  similar  course  when 
sulphurous  acid  without  any  base  is  used ;  indeed,  this  acid  is  well 
known  to  have  a  decomposing  action  upon  many  groups  of  organic 
compounds.  As  a  reducing  agent,  using  the  word  in  its  chemical 
sense,  the  acid  retards  and  limits  the  secondary  changes,  but  it  does 
not  altogether  prevent  them.  The  brown  color  of  pulp  obtained 
by  the  Pictet  process  is  due  in  part  to  the  products  of  the  changes 
set  up  by  the  sulphurous  acid,  as  well  as  to  those  which  are  induced 
by  the  sulphuric  acid  formed  during  this  process.  This  is  shown 
by  the  fact  that  the  addition  to  the  liquor  of  the  very  small  amount 
of  soda  required  to  neutralize  this  sulphuric  acid  does  not  prevent 
the  browning  of  the  pulp. 

The  primary  action  of  a  bisulphite  liquor  in  resolving  wood 
proceeds  upon  the  same  lines  as  that  of  a  solution  of  sulphurous 
acid,  but  the  presence  of  the  base  in  this  combination  materially 
modifies  the  subsequent  course  of  the  reactions.  The  bisulphites 
possess  the  remarkable  property  of  forming,  with  the  aldehydic 
products  of  the  first  stage  of  the  decomposition,  true  double  com- 
pounds which  are  soluble  and  comparatively  stable.  Compounds 
of  this  class  have  been  found  in  the  waste  liquors.  It  is  charac- 
teristic of  the  aldehyde* s  that  they  pass  by  oxidation  into  organic 
acids,  and  in  spite  of  the  presence  of  sulphurous  acid,  which  tends 
to  prevent  oxidation,  there  is  some  formation  of  these  acids. 
Once  formed,  they  displace  the  sulphurous  acid  from  an  equiva- 
lent portion  of  the  base,  and  form  soluble  organic  salts.  By  these 
two  actions  the  bisulphites  take  up  the  products  of  the  resolution 
of  the  wood,  and  prevent  for  the  most  part  the  extreme  degrada- 
tion of  the  products  which  is  characteristic  of  the  water  treatment 
or  of  the  soda  process.  The  combination  of  the  acid  products 
with  the  base  is  shown  by  the  steady  rise  in  the  gas  pressure 
observed  during  the  last  part  of  a  sulphite  cook,  and  which  is 
avoided  by  blowing  off.  It  is  also  showiuby  the  composition  of 
the  waste  liquors,  A.  Ihl  finds  that  the  resinous  matter  obtained 
by  evaporating  these  liquors  consists  mainly  of  the  calcium  salts 
of  acids  similar  to  Arabic  acid,  and  that  .these  acids,  as  indicated 
above,  decompose  carbonates,  sulphites,  and  sulphides. 

An  incidental  advantage  of  considerable  importance  is  obtained 
by  the  use  of  sulphurous  acid  in  connection  with  a  base,  and  is 


184  THE  CHEMISTRY  OF  PAPER-MAKING. 

due  to  the  power  of  this  acid  to  form  with  various  coloring-matters 
compounds  which  are  themselves  colorless.  The  practical  effect 
of  this  latter  action  is  the  production  of  a  fibre  which  may  be  at 
first  of  a  color  as  good  as  that  of  well-bleached  pulp,  although,  as 
in  case  of  all  sulphurous  acid  bleaching,  this  high  color  does  not 
persist  for  any  considerable  length  of  time. 

Although  all  the  bisulphites  act  in  general  in  the  manner 
specified  above,  the  character  of  the  liquor  is  modified  in  several 
important  particulars,  according  as  one  base  or  another  is  in 
combination  with  the  acid.  Bisulphite  of  lime  is  a  very  unstable 
salt  which  upon  being  merely  heated  decomposes ;  one-half  of  the 
acid  being  set  free.  The  resulting  monosulphite  is  practically 
insoluble,  so  that  when,  this  decomposition  occurs  in  the  boiler, 
this  latter  salt  is  precipitated  throughout  the  pulp,  from  which  it 
is  difficult  to  remove  it  by  washing.  Where  lime  liquor  is  used, 
there  is  therefore  more  gas  pressure  in  the  digester,  and  the 
resulting  pulp  is  comparatively  harsh,  hard,  and  transparent.  It 
is  also  more  difficult  to  make  a  straight  lime  liquor  of  high  test 
than  it  is  to  prepare  similar  liquors  from  magnesia  or  soda,  but 
on  account  of  the  insolubility  of  sulphate  of  lime  the  former 
liquors  never  contain  more  than  three-tenths  per  cent,  of  sulphuric 
acid,  while  soda  or  magnesia  liquors  may  contain  an  indefinite 
amount.  In  the  case  of  lime  liquors,  any  excess  of  sulphate  over 
the  amount  given  is  precipitated  and  may  be  settled  out. 

Bisulphite  of  magnesia  is  somewhat  more  stable  than  the  corre- 
sponding lime  salt,  and  its  action  on  the  incrustihg  matter  is 
milder,  but  even  more  effectual.  The  sulphates  or  monosulphites 
which  may  be  present  in  magnesia  liquors  remain  in  solution,  and 
are  easily  washed  out  from  tlie  pulp.  The  resulting  product  is 
much  softer  and  whiter  than  any  which  is  ordinarily  made  with 
lime  without  some  subsequent  treatment.  These  desirable  qualities 
of  magnesia  are  possessed  in  a  still  higher  degree  by  soda.  Sodium 
bisulphite  is  so  permanent  that  it  may  be  easily  obtained  and 
preserved  in  the  crystalline  form.  The  gas  has  so  strong  an 
affinity  for  the  base  that  liquors  of  35°  Be*  may  be  made  without 
difficulty.  Both  the  sulphite  and  sulphate  of  soda  are  very  soluble, 
and  there  is  therefore  ao  precipitation  either  in  the  liquor  appa- 
ratus or  in  the  digester.  Pulp  made  with  soda  liquor  is  white 
and  soft,  and  almost  entirely  free  from  the  last  portions  of 
meiusting  matter. 


THE  SULPHITE  PROCESS.  185 

It  has  been  held  in  some  quarters  that  sulphuric  acid  in  con- 
siderable amount  is  formed  in  the  digester  during  boiling,  but 
numerous  experiments  by  ourselves  and  others  show  that  in  reality 
this  oxidation  of  the  sulphurous  acid  is  very  slight ;  it  is  obviously 
so  when  we  consider  that  making  no  allowance  for  the  chips  and 
liquor  in  the  digester,  but  supposing  the  whole  interior  to  be 
filled  with  air  at  the  ordinary  temperature  and  pressure,  the  total 
amount  of  oxygen  contained  therein  only  amounts  to  22  Ibs.  in 
a  digester  of  a  capacity  of  1200  cubic  feet,  a  quantity  so  small 
when  compared  to  the  weight  of  sulphurous  acid  in  the  liquor  that 
it  may  be  disregarded.  An  additional  proof  is  found  in  the  Pictet- 
Brelaz  process  in  which  it  is  possible  to  recover  as  sulphurous  acid 
95  per  cent,  of  all  the  gas  originally  present  in  the  liquor. 

History.  —  Tilghman  is  said  to  have  spent  about  $40,000  in  ex- 
periments at  a  mill  at  Manayunk,  Pa.  He  boiled  in  long  ten-inch 
cylinders,  lead  lined.  Although  excellent  fibre  was  obtained,  the 
engineering  difficulties  proved  so  serious  that  the  experiments 
were  finally  abandoned. 

After  the  failure  of  Tilghman  to  put  his  process  upon  a  com- 
mercial footing  it  was  taken  up  by  Fry  and  Ekman  at  Bergvik, 
Sweden,  about  1870,  after  a  course  of  experiments  in  -which  nitric 
and  various  acids  and  water  alone  had  been  tried  as  resolving 
agents.  In  1872  the  present  Ekman  process,  using  a  solution  of 
bisulphite  of  magnesia,  was  so  far  developed  that  these  gentlemen 
had  a  three-ton  mill  running  on  a  commercial  basis  with  eight 
small  jacketed  digesters.  The  process  was  worked  secretly 
until  about  1879.  It  was  introduced  into  England  in  a  small 
way  at  Ilford  Mills,  near  London,  after  which,  in  1884,  the  pro- 
prietors of  the  patent  erected  a  large  mill  at  Northfleet,  also  near 
London. 

Although  in  no  way  essential  to  his  process,  Ekman  has  always 
favored  the  preparation  of  this  solution  in  towers.  Those  first  used 
at  Bergvik  were  5  feet  in  diameter,  14  feet  high,  and  filled  above 
the  false  bottom  with  calcined  magnesia.  They  carried  at  the 
top  sprinklers  for  distributing  and  regulating  the  flow  of  water. 

The  next  to  assist  in  the  development  of  the  process  was 
Mitscherlich,  then  professor  of  chemistry  at  Miinden,  and  a  son  of 
the  celebrated  discoverer  of  the  law  of  isomerism.  He  began  his 
experiments  at  the  mill  of  F.  Keferstein,  Ermsleben,  near  the  Hartz 
Mountains,  about  1876,  and  later  went  to  Thode's  Mill,  near 


186  THE  CHEMISTRY   OF  PAPER-MAKING. 

Dresden.  He  did  not  get  started  on  a  commercial  scale  until  about 
1880  or  1881. 

On  the  llth  of  October,  1883,  Moritz  Behrend,  the  lessee  of 
Prince  Bismarck's  mill  at  Coeslin,  disputed  the  validity  of  the 
Mitscherlich  patents.  He  relied  chiefly  upon  the  Tilghman  British 
patent,  No.  2924,  dated  Nov.  9,  1866.  After  a  very  long  trial 
and  examination  of  technical  experts,  the  German  Board  of  Patents 
concluded  that  the  Mitscherlich  process  did  not  differ  from  that 
of  Tilghman  sufficiently  to  entitle  it  to  protection. 

Francke,  in  Gothenburg,  Sweden,  began  his  experiments  about 
1879,  his  attention,  it  is  said,  being  turned  in  this  direction 
through  the  introduction  to  him  of  one  of  Ekman  and  Fry's 
chemists.  He  began  work  in  a  commercial  way  about  1882.  His 
process  has  so  far  secured  no  foothold  in  this  country,  and  presents 
few  points  of  interest.  The  liquor  is  prepared  in  towers,  and  the 
digester  is  a  horizontal  rotary  cylinder,  lead  lined.  The  lining  is 
held  in  place  by  rings  of  various  construction. 

The  Partington  process,  which  was  acquired  by  the  American 
Sulphite  Pulp  Company,  about  1884,  was  one  of  the  first  to  be  intro- 
duced here.  The  liquor  plant  shows  a  radical  departure  from 
those  previously  used,  and  will  be  described  in  detail  under 
Liquor  Making.  The  digesters  are  spherical  rotaries.  The  various 
steps  taken  by  Parti&gton  in  the  development  of  his  system  for 
lining  these  digesters  comprise  one  of  the  most  interesting  studies 
in  engineering  which  the  process  has  shown.  They  will  be  dis- 
cussed at  some  length  in  the  section  given  to  digester  linings. 

McDougall  was  for  some  time  associated  with  Partington,  and 
his  plant  in  1887  differed  little  from  the  last  described,  except  in 
the  method  adopted  for  lining  digesters. 

Various  other  manufacturers  in  different  parts  of  Europe  started 
almost  contemporaneously  with  these  workers.  Graham  in  Eng- 
land, who  had  been  chemist  to  Ekman  and  Fry,  applied  to  digester 
linings  a  method  by  which  the  lead  was  caused  to  adhere  uniformly 
over  the  surface  of  the  iron  shell,  and  worked  out  a  special  modi- 
fication of  the  Ekman  process,  which  consisted  in  re-enforcing  the 
strength  of  the  boiling  liquor  during  cooking  by  fresh  charges  of 
gas.  Graham's  process  has  not  come  into  practical  use,  but  the 
digester  has  been  adopted  by  Ekman,  and  by  some  mills  in  this 
country.  Flodqvist  for  a  time  exploited  the  process  in  which  a 
liquor  containing  both  bisulphite  and  phosphate  of  lime  was  used, 


THE  SULPHITE  PROCESS.  187 

the  liquor  being  made  in  a  series  of  towers,  some  of  which  were 
packed  with  limestone  and  others  with  the  bones  which  furnished 
the  supply  of  phosphate.  Kellner  in  Austria,  who  was  at  that  time 
associated  with  Baron  Hitter,  and  who  is  one  of  the  most  skillful 
chemical  engineers  who  has  turned  his  attention  in  this  direction, 
had  taken  out,  in  1885,  several  patents  covering  a  special  process, 
liquor  apparatus  and  digester,  which  were  then  in  successful 
operation. 

The  difficulties  occasioned  by  the  use  of  an  acid  sulphite  had,  as 
early  as  1880,  led  Cross  to  bring  out  a  process  employing  an 
alkaline  solution  of  sulphite  of  soda  in  iron  digesters,  unlined. 
This  reagent  has  no  effect  on  the  iron,  but  its  use  necessitates  the 
carrying  of  considerably  higher  pressures  than  where  the  bisulphite 
is  used,  the  bleaching  action  of  the  sulphurous  acid  is  much  re- 
stricted, and  the  cost  of  chemicals  much  increased.  There  is, 
moreover,  according  to  our  own  experiments,  a  precipitation  under 
these  conditions  of  free  sulphur  throughout  the  pulp.  The  Pictet- 
Brelaz  process,  on  the  other  hand,  which  was  brought  out  in  1883, 
goes  to  the  other  extreme,  and  instead  of  increasing  the  amount 
of  base  as  Cross  had  done,  does  away  with  it  altogether,  the  wood 
being  boiled  at  a  temperature  never  exceeding  105°  C.,  in  a  solu- 
tion carrying  from  7  to  8  per  cent,  sulphurous  acid. 

The  first  American  paper-maker  to  introduce  the  process  upon 
a  commercial  scale  in  this  country  was  Charles  S.  Wheelwright, 
then  of  Providence,  R.I.  The  Ekman  process  was  the  modifica- 
tion selected,  after  a  visit,  in  1882,  to  the  small  mill  in  which  it 
was  in  operation  at  Bergvik,  Sweden.  Although  the  process  as 
there  shown  was  evidently  very  imperfect  on  the  mechanical  side, 
the  high  grade  of  the  product  encouraged  Mr.  Wheelwright  and 
his  associates  to  erect  on  a  large  scale  the  now  historical  plant  of 
the  Richmond  Paper  Company. 

Pulp  of  the  highest  quality  was  made  almost  from  the  start; 
but  the  mechanical  difficulties  of  working  the  process  on  a  large 
scale  proved  so  serious  that  in  spite  of  his  untiring  energy,  Mr. 
Wheelwright  soon  found  himself  in  almost  the  position  of  the 
original  inventor,  Tilghman.' 

The  towers  filled  with  calcined  magnesia,  as  was  the  case  at 
Bergvik,  gave  endless  trouble  from  the  difficulty  of  regulating  the 
flow  of  water,  from  the  great  tendency  of  the  magnesia  to  soften 
up  and  form, mud,  and  finally,  from  the  liability,  when  the  water 


188  THE  CHEMISTRY  OF  PAPER-MAKING. 

supply  was  temporarily  stopped,  of  the  whole  mass  to  cake  and 
bind  together  through  the  formation  of  monosulphite  of  magnesia. 
These  defects  in  the  apparatus  frequently  made  it  impossible  to 
secure  regular  or  free  draft  up  through  the  tower,  the  output  of 
liquor  was  small,  and  both  its  quantity  and  composition  were 
irregular.  After  trials  on  ;a  Large  scale,  with  many  different  forms 
of  apparatus,  those  difficulties  were  entirely  overcome  r  by  the 
adoption  of  the  apparatus  suggested  by  Catlin.  Obstacles  equally 
serious  were  encountered  in  working  the  digesters,  as  the  engi- 
neering problems  presented  were  such  that  no  precedents  could  be 
found  for  guidance.  Various  forms  of  digester  were  designed  in 
succession  by  Mr.  Wheelwright  to  such  good  effect  that  the  cost 
of  repairs  on  linings  were  in  about  three  years  reduced  from  over 
$10.00  to  about  $L5Q  per  ton  of  product.  Throughout  all  this 
period  of  difficulty  the  product  of  the  mill  was  equal,  if  not 
superior,  to  any  which  has  since  been  produced  here  or  abroad. 

Except  in  a  few  instances  which  will  be  noted,  the  subsequent 
development  of  the  process  in  this  country  has  proceeded  upon 
the  lines  laid  down  in  Europe,  although  numerous  forms  of 
digesters  and  liquor  apparatus  have  appeared.  Two  new  systems, 
those  of  Schenck  and  Crocker^  have  been  developed  commercially, 
and  the  former  bas  been  widely  introduced.  The  main  novelty 
of  the  Schenck  process  is  found  in  the  digester,  which  is  built  up  in 
three-feet  sections  cast  ironi  &  special  bronze.  His  liquor  apparatus 
differs  slightly  from  that  of  Partington,  and  the  general  method 
of  procedure  in  the  process  itself  is  much  the  same.  The  Crocker 
process  differs  from  all  those  before  mentioned  in  that  it  employs 
a  solution  of  bisulphite  of  soda  prepared  by  double  decomposition 
by  treating  bisulphite  of  lime  solution  with  sulphate  of  soda. 

Preparing  Wood.  —  Owing  to  the  great  solvent  power  of  the 
alkali  in  the  soda  process,  comparatively  little  pains  are  necessary 
in  the  preparation  of  the  wood.  In  the  sulphite  process,  however, 
all  portions  of  bark  and  knots  which  go  into  the  digester  are  only 
slightly  acted  upon  by  the  liquor,  and  are  liable  to  cause  dirt  in 
the  pulp.  It  is  a  prime  necessity,  therefore,  that  all  bark  should 
be  carefully  removed  either  by  draw-shaves  or  by  a  barker.  This 
applies  as  well  to  the  light-colored  inner  bark  as  to  the  outer  bark. 
Wherever,  on  account  of  an  old  wound  in  the  tree,  the  bark  is 
turned  inward,  these  portions  are  best  cut  out  by  hand,  since  the 
use  of  the  barker  involves  in  these  cases  an  unnecessary  loss  of 


THE  SULPHITE  PROCESS.  189 

sound  wood.  All  portions  of  wood,  also,  that  are  decayed  or 
badly  stained,  must  be  removed.  A  difference  of  opinion  exists 
as  to  the  proper  method  of  handling  knots.  In  some  mills  it  is 
the  practice  to  remove  all  knots  by  boring ;  but  this  seems  to  us 
objectionable,  since  it  not  only  involves  considerable  labor,  but  is 
liable  to  cause  fine  dirt  in  the  pulp  by  splitting  up  portions  of  the 
knot  into  small  fragments  which  will  get  through  the  screens. 
As  the  sound  knots  are  hardly  softened  at  all  by  the  liquor,  the 
preferable  plan,  in  our  opinion,  is  to  make  no  attempt  to  remove 
them  until  after  the  wood  has  been  brought  to  pulp.  They  are 
thus  left  in  pieces  of  such  large  size  that  they  are  readily  taken 
out  upon  the  screen,  and  all  danger  of  fine  dirt  from  this  cause  is 
avoided.  Rotten  knots  break  up  in  the  cooking  and  subsequent 
operations,  and  should  be  cut  out.  Where  labor  is  sufficiently 
cheap  to  admit  of  its  being  done,  it  is  well  to  have  the  wood 
coming  from  the  chipper  thrown  upon  an  endless  belt,  by  the 
sides  of  which  boys  or  girls  may  be  stationed  to  pick  out  all  knots 
and  unsound  chips.  This  is  the  universal  practice  in  sulphite 
mills  abroad.  Some  of  these  foreign  mills  go  to  the  further  extents 
of  sorting  their  chips  to  size.  We  have  failed  to-  discover  that 
this  offers  any  advantages  to  compensate  for  the  increased  cost. 

In  many  mills  the  wood,  after  leaving  the  chipper,  is  passed 
between  crushing  rolls,  one  running  at  twice  the  speed  of  the 
other,  and  both  covered  with  coarse,  pyramidal  teeth.  A  toothed 
scraper  under  the  bottom  roll  acts  as  a  doctor.  The  advantage  of 
crushing  is  that  it  permits  more  rapid  absorption  of  the  liquor,  so 
that  cooks  can  be  made  more  quickly  and  with  less  danger  of 
leaving  any  of  the  chips  with  a  hard,  red,  central  portion.  The 
knots,  however,  are  likely  to  be  broken  up,  and  the  quantity  of 
wood  which  can  be  cooked  at  one  time  is  somewhat  diminished. 

All  the  chips-cooked  at  one  time  should  be  of  a  single  kind  of 
wood,  and  as  nearly  as  possible  in  the  same  condition  as  regards 
age  and  moisture.  The  treatment  necessarily  varies  for  different 
woods,  and  even  for  the  same  wood!  wh^n  dry  OE  green.  Where 
it  can  be  done,  it  is  advantageous  to  keep  the  wood  in  water  for 
some  time  before  chipping,  as  it  i»  thus  all  brought  to  the  same 
state  of  moisture.  Green  wood  is  more  easily  reduced  by  the 
sulphite  process  than  wood  whieh  ha;s>  l>e«n  seasoned. 

Although  chips  are  used  in  some  instances  where  mills  are 
working  the  Mitscherlich  process,  the  more  general  practice  is  to 


190  THE  CHEMISTRY  OF  PAPER-MAKING. 

cut  the  log  into  discs  1 J  inches  thick  by  gang-saws.  It  is  claimed 
that  in  this  way,  where  the  slow  method  of  packing  the  digester 
by  hand  is  followed,  more  wood  can  be  handled  at  a  boiling,  and 
better  circulation  secured,  than  where  chips  are  used. 

The  use  of  chips,  however,  involves  less  time  and  labor  and  the 
yield  per  cord  is  greater,  as  at  least  10  per  cent,  of  the  wood  must 
be  lost  as  sawdust  when  discs  "are  used.  Where  the  chips  are 
properly  handled,  the  fibre,  for  all  practical  purposes,  should  not 
have  its  length  or  strength  impaired. 

Spruce  is  the  wood  most  commonly  used  in  this  country  for 
making  sulphite  pulp,  but  much  of  the  foreign  fibre  is  made  from 
the  Swedish  fir.  Any  of  the  coniferous  woods  which  are  not  too 
resinous  to  yield  easily  to  treatment  may  be  used  in  place  of 
spruce ;  but  as  each  wood  has  its  own  peculiarities  which  call  for 
differences  in  treatment,  it  is  best  cooked  separately  and  unmixed 
with  other  woods. 

Liquor-Making.  —  The  preparation  of  the  solution  used  in  the 
sulphite  process  depends  upon,  or  is  influenced  by,  several  general 
facts  which  it  is  well  to  recall  here.  When  sulphur  is  heated  in 
the  air,  it  first  melts  to  an  amber-colored  liquid  at  115°  C. ;  as  the 
heating  is  continued,  the  melted  sulphur  gradually  darkens  in  color 
and  becomes  very  thick  and  tenacious ;  at  a  still  higher  tempera- 
ture it  partially  regains  its  fluidity;  and  at  about  300°  C.  begins 
to  vaporize.  If  this  dark,  reddish  brown  vapor  is  allowed  to  cool, 
the  sulphur  is  deposited  either  in  the  powdery  form  as  flowers  of 
sulphur,  or  as  a  liquid,  according  to  conditions  of  temperature. 
Sulphur  burns  in  the  air  with  a  blue  flame  tipped  with  white, 
forming  sulphurous  acid  gas,  SO2.  This  gas  is  very  soluble  in 
water,  one  volume  of  water  at  zero  dissolving  seventy-nine  volumes 
of  the  gas.  The  facility  with  which  the  gas  is  absorbed  varies 
greatly  with  the  temperature  and  pressure,  diminishing  rapidly  as 
the  temperature  rises ;  while  at  a  given  temperature  the  amount 
absorbed  varies  directly  as  the  pressure.  The  moist  gas  has  a 
very  strong  affinity  for  oxygen,  with  which,  in  the  presence  of 
water,  it  combines  to  form  sulphuric  acid,  H2SO4.  Since  only 
about  one-fifth  of  the  volume  of  air  is  oxygen,  and  since  for  every 
volume  of  oxygen  consumed  in  the  first  instance  by  the  burning 
sulphur  there  is  formed  only  an  equal  volume  of  sulphurous  acid, 
the  strongest  gas  which  can  possibly  be  made  in  practice  can  only 
contain  about  20  per  cent.  SO2.  As  a  matter  of  fact,  the  content 


THE  SULPHITE  PROCESS.  191 

of  SOa  rarely  reaches  10  per  cent.  The  gas  going  into  the  absorp- 
tion apparatus  is  therefore  so  largely  diluted  with  the  waste  nitro- 
gen from  the  air  and  the  unconsuined  oxygen,  that  the  absorption 
proceeds  at  a  much  slower  rate  than  would  be  the  case  could  the 
pure  gas  be  obtained,  and  there  is  even  a  considerable  tendency 
for  the  waste  gases  to  sweep  the  free  sulphurous  acid  out  of  a 
strong  liquor  through  or  over  which  they  pass. 

The  different  jForms  of  apparatus  in  which  the  liquor  is  prepared 
may  be  divided  for  our  present  purpose  into  two  classes  :  those  in 
which  the  gas  is  brought  in  contact  with  water  containing  the 
base  in  solution  or  suspension,  and  those  in  which  the  gas  and 
water  come  in  contact  with  the  carbonate  of  the  base,  which, 
instead  of  being  minutely  subdivided,  is  present  in  lumps  of  con- 
siderable size.  In  the  former  case  the  gas  is  first  dissolved  by  the 
water  forming  the  true  sulphurous  acid,  H2SO3.  This  acid  immedi- 
ately reacts  with  the  base  to  form  the  monosulphite.  If  the  base 
is  soda,  the  sulphite  remains  in  solution,  and  the  same  is  true  to  a 
considerable  extent  of  sulphite  of  magnesia.  Sulphite  of  lime, 
however,  is  very  insoluble,  one  part  of  the  salt  requiring  for  its 
solution  800  parts  of  water,  so  that  when  milk  of  lime  is  used,  the 
sulphite  is  precipitated  in  the  crystalline  form  as  fast  as  it  is  made. 
The  formation  of  monosulphite  goes  on  until  all  the  lime  is  pre- 
cipitated. As  the  absorption  of  gas  continues,  the  monosulphite 
gradually  takes  up  an  additional  equivalent  of  the  acid,  forming  the 
bisulphite,  which  is  readily  soluble.  Unless  the  quantity  of  base  is 
excessive,  nearly  the  whole  of  the  lime  is  thus  brought  into  solu- 
tion. Owing  to  the  great  tendency  of  sulphurous  acid  to  oxidize 
with  the  formation  of  sulphuric  acid,  and  the  difficulty  of  properly 
regulating  the  supply  of  air,  thero  is  always  formed,  in  practice, 
with  the  bisulphite,  more  or  loss  sulphate  which,  being  insoluble, 
remains  in  the  liquor  as  a  white  precipitate,  which  may  be  readily 
distinguished  from  the  still  more  insoluble  monosulphite  by  the 
yellow  color  and  more  granular  appearanqe  of  the  latter.  In 
the  second  type  of  absorption  apparatus  the  gas  is  absorbed  by 
the  water  as  before,  and  the  solution  thus  formed  reacts  upon  the 
carbonate  which  is  present  in  the  form  of  limestone  or  dolomite, 
forming  sulphite  of  lime  and  setting  free  carbonic  acid,  as  shown 
in  the  reaction  — 

HjS08  +  CaC08  =  CaS03  +  HaO  +  CO,. 


192 


THE  CHEMISTRY  OF  PAPER-MAKING. 


After  a  time  the  surface  of  the  limestone  becomes  more  or  less 
crusted  with "the  sulphite,  and  as  more  gas  is  absorbed  this  crust  is 
brought  into  solution  as  bisulphite.  There  is,  however,  in  such 
forms  of  apparatus  a  tendency  for  both  these  reactions  to  proceed 
simultaneously  when  there  is  a  free  supply  of  gas;  that  is,  fresh 
portions  of  limestone  are  being  changed  to  monosulphite,  while  at 
the  same  time  portions  of  monosulphite  are  being  dissolved  by  the 
acid  solution.  The  formation  of  sulphate  of  lime  proceeds  here  as 
in  the  former  case,  but  considerable  portions  of  it  adhere  to  the 
limestone  as  a  crust. 

The  absorption  of  gas  takes  place  only  at  the  surfaces  of  contact 
between  gas  and  liquor,  so  that,  other  things  being  equal,  the  most 
efficient  apparatus  is  the  one  in  which  the  liquid  presents  the  great- 
est amount  of  surface  to  the  action  of  the  gas. 

Sulphur  Burning.  —  Sulphur  is  found  in  the  market  in  three 
grades,  known  as  firsts,  seconds,  and  thirds,  the  only  differences  in 
the  three  grades  being  those  of  color  and  in  the  amount  of  dirt  and 
ash  present.  In  seconds  the  ash  rarely  exceeds  £  per  cent.  A 
form  of  sulphur  known  as  Chance  recovered  sulphur  has  been 
lately  put  upon  the  market,  and  is  for  all  practical  purposes 
chemically  pure.  The  following  are  analyses  made  in  our  labora- 
tory of  commercial  sulphur  :  — 


Seconds. 

Chance  recov- 
ered sulphur. 

Moisture     

0.01 

020 

0.06 

Foreign  matter,  insoluble  in  carbon 
disulpbiae    ...                         . 

0  06 

0  76 

0.016 

Sulphur      '.                   .     .       • 

90  93 

99  04 

99  82 

99.984 

A'feh   .         *     . 

0  37 

0  12 

0  012 

Thirds  usually  contain  about  1  per  cent,  of  foreign  matter,  but  the 
proportion  runs  in  rare  cases  as  high  as  3  per  cent. 

Seconds  and  thirds  are  most  commonly  used  in  making  sulphite 
liquors ;  but  in  many  Eastern  mills  recovered  sulphur  is  now  being 
used,  on  account  of  its  greater  purity  and  the  fact  that  because  it 
is  shipped  in  bags  it  can  be  handled  more  easily  than  the  Sicilian 
sulphur,  which  comes  in  bulk.  In  the  West  considerable  Utah 
sulphur  is  now  being  used. 


THE  SULPHITE  PROCESS.  393 

The  dimensions  and  construction  of  sulphur  furnaces  show 
great  variations  in  different  mills.  The  best  styles  conform  to 
the  following  requirements:  They  should  be  as  nearly  air  tight 
as  it  is  possible  to  make  them,  except  at  those  points  where  pro- 
vision is  made  for  admitting  and  regulating  the  supply  of  air ;  the 
pan  should  be  perfectly  level,  and  of  such  size  that  not  more 
than  2J  Ibs.  of  sulphur  need  be  burned  per  square  foot  of  pan 
surface  per  hour ;  the  pan  should  be  so  supported  by  foundations 
as  to  leave  an  air-space  under  its  entire  length,  in  order  to  keep 
it  as  cool  as  possible  ;  and  the  entire  furnace  should  be  so  con- 
structed as  to  avoid  as  far  as  may  be  the  danger  of  overheating. 


FIG.  19.  — RETORT  SULPHUR  FURNACE. 

The  retort  style  of  furnace  shown  in  Fig.  19  is  in  very  common 
use;  and  where  pains  are  taken  to  have  the  door  fit  closely,  this 
furnace  is  perhaps  as  satisfactory  as  any  for  plants  of  moderate 
size.  The  body  of  the  furnace  is  in  one  piece,  and  is  made  of 
cast  iron,  an  inch,  or  better,  an  inch  and  a  half  in  thickness.  It 
is  about  8  feet  6  inches  long,  and  2  feet  6  inches  wide,  on  the 
outside  ;  the  inside  perpendicular  being  18  inches.  The  8-inch 
pipe  by  which  the  gases  leave  the  furnace  is  either  bolted  to  the 
back  of  the  furnace,  as  high  as  possible  above  the  pan,  or  else  to 
the  top  of  the  arch  near  that  end.  A  second  casting  with  guides 
and  bearings  for  the  door  is  bolted  to  the  perpendicular  face  which 
forms  the  open  end  of  the  retort.  The  retorts  are  supported  by 
brick  foundations  which,  when  properly  built,  contain  an  air-space 
extending  along  the  bottom  or  pan  of  the  furnace.  The  retorts 


194 


THE  CHEMISTRY  OF  PAPER-MAKING. 


are  sometimes  surrounded  by  a  water-jacket ;  and  in  other  cases  a 
shower  of  water  is  delivered  from  a  sprinkler  pipe  upon  the  top 
of  the  furnace. 

Similar  furnaces,  but  with  doors  which  can  be  closed  air-tight, 
are  used  for  burning  sulphur  under  pressure,  as  shown  in  Fig.  33. 

Eknaan  introduced  a  furnace  built  of  |-inch  boiler  iron,  riveted 
together,  and  caulked  air-tight.  The  dimensions  of  the  pan  are 
about  2  feet  3  inches  by  7  feet,  and  the  height  of  the  furnace 
about  5  feet.  The  only  novelty  in  the  furnace  is  found  in  the  layer 


FIG.  20.  —  MODIFIED  EKMAN  FURNACE  —  SECTION. 

of  broken  fire-brick  resting  on  inclined  grate-bars.  An  inclined 
cast-iron  plate  extends  from  the  front  of  the  furnace  below  the 
grate  and  just  above  the  door,  at  a  distance  about  two-thirds  of 
the  length  of  the  furnace.  The  object  of  the  brick,  which  are 
loosely  arranged  in  a  layer  about  9  inches  deep,  is  to  cause  a  more 
perfect  mingling  of  the  air  and  any  sulphur  vapor  present,  thus 
insuring  more  perfect  combustion  and  less  subliming.  The  thin 
iron  walls  of  the  furnace  radiate  heat  rapidly,  so  that  it  is  kept 
quite  cool.  Ekman  claims  to  reduce  the  amount  of  SO8  formed 
about  one-half  by  the  use  of  the  fire-brick ;  but  where  a  furnace  is 
properly  run,  there  should  be  no  vapor  of  sulphur  passing  off,  and 


THE  SULPHITE  PROCESS. 


195 


if  an  excess  of  air  is  admitted,  much  of  the  SO3  is  formed  beyond 
the  furnace  in  the  absorption  apparatus. 

Figs.  20  and  21  show  an  improved  style  of  Ekman  furnace  built 
of  cast-iron  in  sections  which  are  bolted  together.  The  joints  at  the 
flanges  are  made  air-tight  by  some  form  of  asbestos  packing.  The 
layer  of  brick  rests  upon  wrought-iron  grate-bars,  which  in  this 
furnace  are  not  inclined.  The  door  swings  inward,  and  is  so 
balanced  that  it  closes  when  left  open.  The  amount  of  air  ad- 
mitted is  regulated  by  screwing  in  the  handle  which  passes  through 
the  ball  counterpoise  on  the  door,  so  that  the  end  of  the  handle 


FIG.  21. — MODIFIED  EKMAN  FURNACE — LONGITUDINAL  SECTION. 

strikes  the  furnace  and  holds  the  door  before  the  latter  has  swung 
completely  to.  Any  desired  open  space  may  thus  be  left  below 
the  door.  This  furnace  has  two  wrought-iron  pans. 

Furnaces  of  about  the  dimensions  given  in  Figs.  20  and  21  are 
sometimes  built  with  brick  walls  lined  with  fire-brick.  The  back  is 
sometimes  in  these  cases  made  of  an  iron  plate  or  casting,  and  the 
top  and  front  are  nearly  always  so  constructed.  L  Some  Mitscherlich 
mills  use  a  furnace  about  2  feet  6  inches  wide,  8  feet  long,  and  7 
feet  high;  The  furnace  is  charged  through  an  8-inch  iron  pipe, 
passing  at  an  angle  through  the  wall,  and  which  is  ordinarily  kept 
closed  by  a  flange  or  cap. 


196  THE  CHEMISTRY  OF  PAPERS  AKIN  G. 

In  starting  up  a  sulphur  furnace  of  the  usual  type  sufficient  sul- 
phur is  thrown  in  to  form,  when  melted,  a  layer  over  the  bottom 
about  one  inch  in  depth.  A  red-hot  bolt  thrown  into  the  furnace 
starts  the  combustion.  With  retort  furnaces,  unless  working  un- 
der pressure,  the  air  supply  is  regulated  by  the  extent  to  which  the 
door  is  closed.  The  open  space  under  the  door  should  never  be 
more  than  one-quarter  of  an  inch  high,  and  with  most  of  these  fur- 
naces sufficient  air  can  generally  work  its  way  in  through  the 
cracks  around  the  door.  (  In  the  Mitscherlich  and  some  other  fur* 
naces  the  doors  in  front  are  made  air  tight  and  the  air  supply  is 
admitted  through  a  set  of  air-holes  the  size  of  which  is  regulated 
by  a  sliding  damper.  Some  such  plan  as  this  is  to  be  recommended 
in  order  to  properly  control  the  air  supply.1 

The  most  common  way  of  keeping  up  the  supply  of  sulphur  is 
for  the  workman  to  raise  the  furnace  door  and  throw  in  a  few 
shovelfuls  as  needed.  The  door  is  thus  opened  to  its  fullest 
extent  at  frequent  intervals,  and  each  time  it  is  raised  there  is 
a  great  rush  of  air  into  the  furnace  and  through  the  apparatus. 
In  consequence  of  this  the  gas  is  much  diluted,  even  and  regular 
absorption  is  well-nigh  impossible,  and  an  excessive  and  unneces- 
sary amount  of  SO3  is  formed.  It  is  much  better  to  give  the  fur- 
nace a  considerable  supply  of  sulphur  at  a  time  and  to  make  the 
intervals  of  charging  as  few  as  possible.  In  working  the  retorts 
under  pressure  they  are  charged  at  intervals  of  about  four  hours 
with  200  Ibs.  of  sulphur.  Kellner,  in  order  to  avoid  undue  excess 
of  air,  puts  the  sulphur  in  a  hopper  on  top  of  the  furnace,  the  hop- 
per then  being  closed  at  the  top  and  the  charge  fed  in.  Mitscher- 
lich  feeds  through  the  top  or  side  of  the  furnace  in  something  the 
same  way.  Any  hoppers  or  pipes  in  this  position  must  be  so 
arranged  as  to  be  kept  cool,  and  must  have  delivery  pipes  of  good 
diameter,  as  otherwise  there  is  danger  that  the  sulphur  will  become 
so  heated  as  to  pass  into  the  thick  and  tenacious  condition.  Where 
a  number  of  furnaces  deliver  into  one  gas  main  they  should  be 
charged  in  regular  order,  so  that  the  gas  may  be  kept  of  nearly 
constant  composition. 

The  whole  secret  of  burning  sulphur  for  the  preparation  of  sul- 
phite liquors  lies  in  the  proper  regulation  of  the  supply  of  air.  In 
order  to  convert  one  pound  of  sulphur  into  sulphurous  acid  there 
is  required  just  one  pound  of  oxygen,  or  the  amount  of  this  gas 
contained  in  53.81  cubic  feet  of  air.  If  much  more  is  admitted, 


THE  SULPHITE  PROCESS.  197 

and  especially  if  the  air  is  at  all  moist,  there  is  formed  SO3  and  sul- 
phuric acid,  which  corrodes  the  pipes  and  causes  a  considerable  loss 
of  both  lime  and  sulphur.  The  composition  of  the  liquor  under 
these  circumstances  is  subject  to  constant  variation.  When  dolo- 
mite is  used  as  a  base  the  proportion  between  the  lime  and  mag- 
nesia in  the  liquor  is  made  to  vary  as  more  or  less  lime  is  thrown 
down  as  sulphate,  and  where  magnesia  or  soda  is  used  the  sul- 
phate causes  even  more  trouble  by  remaining  in  solution  and 
giving  to  the  liquor  a  fictitious  strength.  Any  considerable  excess 
%  of  air  is  liable  also  to  cause  over-heating  of  the  furnace  and  conse- 
quent sublimation  of  the  sulphur.  More  sulphur  is  vaporized  than 
can  be  burned  and  the  unconsumed  vapor  passes  onward  with 
the  gas  until  it  strikes  the  colder  portions  of  the  pipes  or  cooler, 
where  it  condenses,  clogging  the  pipes  and  causing  the  formation 
of  polythionic  acids,  as  pointed  out  below. 

Sublimation  similarly  occurs  if  for  any  reason  the  air  supply  is 
unduly  curtailed  after  the  furnace  has  become  warmed  up,  since 
under  these  circumstances  there  is  not  enough  air  to  combine  with 
all  the  vapor. 

Colefax  and  others  have  shown  that  sulphurous  acid  acts  on  sul- 
phur at  the  ordinary  temperature  even  in  the  dark  to  form  thio- 
sulphuric  and  polythionic  acids.  This  action  takes  place  still  more 
rapidly  at  temperatures  as  high  as  80°  or  90°  C.  These  acids  are 
very  unstable  and  in  most  cases  decompose  on  being  heated  into 
sulphur,  SO2  and  SO3.  The  thiosulphates  decompose  in  the  pres- 
ence of  stronger  acids  into  sulphur  and  SO2.  Where  these  acids 
are  formed,  as  is  the  case  when  sublimation  and  over-heating 
occur,  a  liquor  is  produced  from  which,  during  the  boiling  opera- 
tion, sulphur  separates  out  and  is  precipitated  on  the  pulp.  Owing 
to  the  insolubility  of  sulphur  it  is  almost  impossible  to  remove  it 
in  this  event,  and  its  presence  makes  trouble  when  the  pulp  is 
used,  the  sulphur  itself  rotting  the  wire  cloth  and  the  sulphuric 
acid  formed  by  oxidation  rotting  the  canvas  felts.  According  to 
Mitscherlich  and  others  the  presence  of  these  higher  acids  of  sul- 
phur will  even  completely  spoil  an  entire  cook. 

The  conditions  under  which  a 'burner  is  working  may  generally 
be  inferred  with  sufficient  accuracy  from  the  appearance  and  char- 
acter of  the  flame.  When  the  sulphur  is  burning  properly  the 
flame  is  a  lazy  blue  one,  sometimes  tipped  with  white.  The  occur- 
rence of  brown  fumes,  which  are  the  wnconsumed  sulphur  vapor, 


198  THE  CHEMISTRY  OF  PAPER-MAKING. 

indicates  that  the  furnace  is  too  hot,  probably  because  of  too  much 
air,  and  that  sublimation  is  likely  to  occur. 

The  furnace  must  be  cleaned  as  often  as  any  considerable  quan- 
tity of  slag  and  ash  accumulates  in  the  pan,  and  the  cleaning  must 
be  done  while  the  furnace  is  still  hot,  since  the  ash  will  otherwise 
be  so  bound  together  by  the  sulphur  remaining  in  it  that  it  can 
hardly  be  removed  at  all. 

Although  sulphur-burning  is  an  apparently  simple  operation,  it 
requires  a  considerable  degree  of  skill  and  careful  attention  on  the 
part  of  the  workman.  Without  these,  much  more  sulphur  than  is 
needed  will  be  burned,  and  the  excess  is  more  than  likely  to  cause 
not  only  loss  but  trouble  all  through  the  process.  The  workman 
should  aim  to  keep  the  gas  as  strong  as  possible  and  to  avoid  irreg- 
ularity in  its  composition.  He  can  only  do  this  by  charging  the 
furnace  in  a  regular  and  methodical  way  and  by  admitting  the 
smallest  possible  amount  of  air  required  to  burn  the  sulphur. 

Copper  or  iron  pyrites  are  burned  in  place  of  sulphur  in  many 
foreign  mills,  and  they  have  lately  been  adopted  in  one  or  two 
mills  here.  Pyrites  burners  are  considerably  more  difficult  to 
handle  than  sulphur  furnaces,  and  they  can  only  be  worked  to 
advantage  where  a  number  of  burners  are  grouped  together  so  that 
a  gas  of  even  composition  may  be  secured.  There  is  considerable 
liability  that  the  burners  may  become  over-heated  locally,  and 
where  such  over-heating  occurs  slags  form  which  are  difficult  to 
remove  and  which  clog  the  draft.  The  most  serious  objection  to 
the  use  of  pyrites  is  due  to  the  fine  dust  which  is  earned  along 
by  the  burner  gas,  and  which,  unless  entirely  removed,  causes  dirt 
in  the  liquor  and  in  the  pulp.  It  is  usually  held  back  by  passing 

the  gas  in  a  very  slow  stream 
through  long  dust  flues  of  large 
area. 

The  ordinary  sorts  of  pyrites 
are,  before  being  burned,  broken 
either  by  hand  or  some  form  of 
crusher  into  pieces  of  small  size, 

FIG.  22. -FREIBERG  PYRITES  BURNER.     the  harder  sorts  bein£  reduced 

to  the  size  of  walnuts,  while  the 

softer  kinds  may  be  left  in  larger  lumps.  The  lumps  are  burned 
on  grate  bars  in  brick  kilns  or  furnaces  of  the  general  construction 
shown  in  Fig.  22,  and  fitted  with  doors  for  charging,  regulating 


THE  SULPHITE  PROCESS. 


199 


the  supply  of  air  and  removing  the  cinders.  Fig.  22  represents 
two  Freiberg  burners,  one  being  shown  in  front  elevation  and  the 
other  in  sectional  elevation.  This  furnace  is  especially  adapted  for 
easily  burning  ores.  The  burner  is  charged  through  the  hole  in 
the  top  and  the  ore  rests  upon  the  triangular  grate  bars.  The  round 
bars  just  above  the  grate  may  be  worked  back  and  forth  from  the 
front  of  the  furnace  and  serve  both  to  break  up  the  ore  and  to  sup- 
port it  while  drawing  cinders.  S  is  the  entrance  to  the  gas  flue 
built  into  the  brickwork  back  of  the  furnace.  A  small  percentage 


FIG.  23.  —  SECTION. 


FlG.  24.  —  LONGITUDINAL 

SECTION. 


© 


FIG.  25.  —  PLAN. 
FIGS.  23,  24,  25. — THE  MITSCHERLICH  PYRITES  BURNER. 

of  copper  is  usually  present  in  the  cinder  from  iron  pyrites  and  its 
extraction  partially  repays  the  cost  of  working  the  pyrites. 

The  Mitscherlich  pyrites  burners  are  shown  in  sections  in  Figs. 
23  and  24,  and  in  plan  in  Fig.  25.  They  are  about  1.5  metres 
square  in  the  clear  and  are  lined  with  Chamotte  brick.  The  top 
is  a  flat  arch  with  a  central  opening  for  the  escape  of  the  gas 
into  the  space  between  this  inner  and  the  upper  arch.  The  upper 
arch  has  two  openings.  Two,  three,  or  more  burners,  according  to 
the  size  of  the  works,  are  built  side  by  side,  or  back  to  back.  Two 
gas  flues  are  built  over  the  burners  and  the  openings  through  the 
upper  arch  make  into  these  flues.  Any  furnace  may  be  cut  out  by 
closing  these  openings  by  means  of  sand  lutes,  as  shown  in  the 


200  THE  CHEMISTRY   OF  PAPER-MAKING. 

drawings.  The  space  between  the  two  arches  prevents  the  burn- 
ers from  becoming  too  cool. 

The  grate,  which  is  not  shown,  is  about  0.5  metre  from  the  floor, 
and  is  composed  of  square  bars  which  may  be  turned  by  a  key 
from  the  front  in  order  to  shake  down  cinders.  The  doors,  which 
are  in  front,  are  luted  with  clay  or  else  smeared  all  over  with  this 
material. 

For  carrying  the  gas  away  from  the  sulphur  furnace  iron  pipes 
may  be  used  as  far  as  the  cooler,  as  the  hot,  dry  gas  has  little  effect 
on  this  metal.  The  cooler,  and  all  pipes  beyond,  should  be  of 
lead.  It  is  necessary  that  the  pipes  should  be  free  from  all  curves 
in  which  the  sublimed  sulphur  might  lodge  beyond  easy  reach, 
and  at  all  bends  or  angles  crosses  should  be  used  to  give  easy 
access  to  the  interior  of  the  pipes.  The  flues  from  pyrites  burners, 
for  a  considerable  distance  at  least,  are  usually  built  of  bricks  which 
have  been  soaked  in  coal-tar  and  which  are  laid  in  a  mixture  of 
tar  and  sand.  As  already  pointed  out,  it  is  absolutely  necessary  to 
lead  the  gas  from  pyrites  burners  through  a  dust  chamber  in  order 
to  avoid  dirt  beyond.  This  chamber,  which  is  usually  built  high 
enough  to  admit  a  man,  is  divided  by  numerous  partial  partitions 
so  that  it  forms  a  long  flue  through  which  the  gas  slowly  passes 
backwards  and  forwards  till  it  reaches  the  exit  pipe.  Similar 
chambers  of  smaller  size  and  built  of  unplaned  plank  may  be  used 
to  advantage  where  the  gas  is  obtained  from  sulphur.  The  rough 
surface  of  the  wood  catches  the  floating  sulphur  and  also  removes 
most  of  the  SO3.  The  chamber  should  be  placed  between  the  fur- 
nace and  the  cooler. 

The  Ritter-Kellner  filtering-tower,  which  is  shown  in  section  and 
plan  in  Figs.  26  and  27,  is  also  well  adapted  to  hold  back  sulphuric 
acid  and  sublimed  sulphur.  The  tower  is  built  of  brick  laid  in 
coal  tar  and  sand,  and  is  divided  into  three  compartments,  which 
are  covered  by  a  slab  of  slate.  The  central  shaft  has  a  false  bottom, 
and  is  nearly  filled  with  limestone,  with  which  the  sulphuric  acid 
combines  to  form  sulphate  of  lime.  The  tower  is  washed  out  from 
time  to  time  by  a  copious  stream  of  water. 

The  means  of  securing  draft  through  the  furnaces  and  the  rest 
of  the  apparatus  varies  with  the  form  of  absorption  apparatus  which 
is  employed.  The  method  employed  by  Mitscherlich  will  be  dis- 
cussed when  we  come  to  the  consideration  of  the  tower.  When 
the  gas  has  to  be  forced  through  a  volume  of  liquid  some  form  of 


THE  SULPHITE  PROCESS.  201 

direct-acting  pump  is  necessary,  and  the  draft  is  maintained,  either 
as  in  the  case  of  the  Partington  apparatus,  by  sucking  the  waste 
gases  from  the  tanks,  or,  as  in  McDougall's  system,  by  forcing  air 
into  the  furnace.  Considerably  more  power  is  required  in  the  last 
case.  In  other  forms  of  apparatus,  like  that  of  Catlin  or  the  later 


FIG.  26.  —  THE  KELLNER  FILTERING-TOWER  —  SECTION. 

form  patented  by  McDougall,  an  ordinary  fan  blower  may  be  used, 
since  in  these  cases  the  passage  of  the  gas  is  not  impeded.  Wher- 
ever their  use  is  thus  indicated  such  blowers  are  to  be  preferred, 
as  for  the  same  volume  of  air  moved  the  cost  of  the  blower  is 
much  less,  while  it  has  fewer  working  parts,  and  can  be  run  and 


202 


THE  CHEM1STHT  OF  PAPER-MAKING. 


maintained  more  cheaply.  The  shell  should  be  lined  with  6-lb. 
lead,  fastened  to  the  iron  by  copper  rivets,  and  all  rivet  heads 
should  be  carefully  burned  over  with  lead.  The  wheel  and  all 
other  internal  parts  should  be  of  suitable  acid-resisting  bronze. 


FIG.  27. — THE  KELLNER  FILTERING-TOWER  —  PLAN. 

The  blower  is  best  placed  before  the  coolers,  where  it  takes  the  hot 
gas  coming  from  the  furnaces. 

It  has  been  already  pointed  out  that  the  r,ate  of  absorption  and 
the  quantity  of  'the  gas  dissolved  by  water  are  mainly  dependent 
upon  the  temperature,  the  quantity  of  gas  absorbed  decreasing 
rapidly  as  the  temperature  rises,  as  shown  below :  — 


Temp. 

o°c. 

20°  " 
40°  « 


1  vol.  of  water 
dissolves  SO2. 

79.789  vols. 
39.374     " 
18.766     « 


1  vol.  of  the  solution 
contains  SO2. 

68.861  vols. 
36.206     " 
17.013     " 


It  is  therefore  necessary,  in  order  to  obtain  the  best  results  in 
liquor-making,  that  cold  water  should  be  used,  and  that  the  tem- 
perature of  the  gas  should  not  be  above  10°  to  15°  C.  Where  the 
gas  is  carried  in  a  slow  stream  through  a  considerable  length  of 
cast-iron  pipe  exposed  to  the  air,  it  will  generally  be  sufficiently 
cool,  except  on  the  warm  days  of  summer.  In  some  foreign  mills 
the  cooling  surface  of  the  pipe  is  increased  very  largely  by  numer- 
ous flanges  cast  on  the  pipe.  It  is  desirable  in  most  systems  to 
have  the  liquor  plant  as  compact  as  possible,  and  for  this  reason 
the  cooler  pipes  are  often  arranged  over  the  furnace,  as  in  Fig.  33, 
pages  211,  212.  The  pipes  are  then  either  cooled  by  water-jackets 
or  by  a  stream  of  water  trickling  over  them. 

Fig.  28  shows  in  section  a  very  efficient  and  compact  form  of 
cooler,  which  is  due  to  Wheelwright.   It  consists  of  a  tight  wooden 


THE  SULPHITE  PROCESS.  203 


box  about  12  feet  long,  3  feet  wide,  and  3  feet  high.  Twelve 
4-inch  lead  pipes  are  arranged  in  the  box  as  shown,  and  pass 
through  the  ends,  where  they  are  flanged  over  and  burned  to  the 
half-inch  lead  with  which  the  ends  of  the  box  are  covered  on  the 


FIG.  28. — THE  WHEELWRIGHT  COOLER. 


outside.  A  gas  chamber,  built  of  half-inch  lead  and  fitted  with  a 
trap  for  condensed  sulphuric  acid  and  with  a  pipe  for  gas,  is  bolted 
to  each  end  of  the  cooler.  The  box  is  kept  filled  with  cold  water, 
which  constantly  flows  in  through  the  supply  pipe.  This  apparatus 
presents  a  large  cooling  surface,  and  the  current  of  gas  moving 
through  the  pipes  is  very  slow.  It  is  easily  cleaned,  and  condenses 
and  holds  back  most  of  the  sulphuric  acid. 

Still  another  cooler  is  shown  on  page  211  in  connection  with  the 
Ritter-Kellner  liquor  apparatus.  This  is  a  more  expensive  form 
than  the  one  just  shown,  and  on  account  of  the  cross  tubes  in  the 
cooler  pipes  the  latter  cannot  be  readily  cleaned.  Difficulty  from 
this  cause  is  avoided  by  the  inventors  by  first  passing  the  gas 
through  a  filtering-tower,  which  keeps  back  the  sublimed  sulphur. 

Absorption  Apparatus.  —  As  already  stated  in  an  earlier  para- 
graph, the  different  forms  of  apparatus  in  which  the  bisulphite 
solution  is  prepared  may  be  conveniently  considered  with  refer- 
ence to  two  general  types,  —  first,  those  in  which  the  gas  is  brought 
in  contact  with  water  holding  the  base  in  suspension  or  solution, 
and  second,  those  in  which  the  gas  and  water  react  upon  the  car- 
bonate of  the  base,  which  is  present  in  lumps  of  considerable  size. 
To  the  first  class  belong  the  apparatus  of  Partington,  McDougall, 
Catlin,  and  others,  while  in  the  second  class  are  found  the  towers 
of  Mitscherlich,  Francke,  and  Kellner,  and  the  modified  towers  or 


THE  CHEMISTRY  OF  PAPER-MAKING. 


tank  system  of  the  last-named  chemist.  The  later  form  of  Ekman 
tower  combines  in  a  measure  the  features  common  to  both  classes. 
The  tower,  as  the  oldest  and  in  some  respects  the  simplest  form 
of  absorption  apparatus,  will  be  considered  first.  It  consists  essen^ 
tially  of  a  high  wooden  shaft,  which  may  be  of  various  dimensions 
and  which  is  usually  of  circular  section.  To  prevent  leakage  the 
joints  are  often  stuffed  with  oakum  and  painted  with  tar.  Several 
of  these  towers  are  commonly  grouped  together  and  surrounded 
and  supported  by  a  scaffolding  braced  by  guy  ropes.  Near  the 
bottom  of  each  tower  is  a  heavy  grating  or  false  bottom.  In  the 
high  Mitscherlich  towers  the  strain  upon  the  grating  is  relieved 
by  having  the  main  weight  of  the  stone  sustained  by  two  heavy 
timbers,  which  pass  through  the  walls  of  the  tower  about  two  feet 
above  the  false  bottom  and  which  are  supported  from  the  outside. 
The  towers  are  nearly  filled  with  lumps  of  limestone  or  dolomite. 
In  Germany  a  special  form  of  porous  limestone  is  preferred,  but 
most  of  the  similar  material  found  in  this  country  contains  rather 
too  much  iron  to  be  well  suited  to  this  purpose,  and  on  that  account 
the  ordinary  dense  limestones  are  commonly  made  use  of  here. 
Dolomite  is  really  the  best  stone  for  use  in  the  tower,  especially  if 
a  dolomite  is  selected  which  pits  as  it  is  eaten  away  by  the  acid. 

In  all  forms  of  towers  the  gas  from  the  furnaces  enters  below  the 
grating  and  meets,  in  its  ascent,  the  descending  water,  which  is 
spread  over  large  surfaces  of  the  stone  in  a  thin  film  so  that  the 
gas  is  rapidly  absorbed.  The  water  is  delivered  at  the  top  through 
a  large  sprinkler  arranged  to  secure  even  and  regular  distribution 
of  the  water.  Many  different  styles  of  sprinkler  are  in  use,  some 

mills  using  the  crude  rose  made  of 
lead,  while  others  have  distributing 
systems  of  pipe  similar  to  those  em- 
ployed on  the  Glover  and  Gay-Lussac 
towers  in  the  manufacture  of  sulphu- 
ric acid.  In  other  cases  the  water  is 
delivered  suddenly  in  some  quantity 
at  intervals  of  a  minute  or  two,  either 
by  a  tilting-tank,  as  in  Fig.  29,  or 
29  ky  apparatus  embodying  the  principle 

of  the  Tantalus  cup,  Fig.  30,  which 
empties  suddenly  as  soon  as  the  siphon  is  primed.  The  sudden 
rush  and  splashing  of  the  water  is  thought  to  secure  better  results 


THE  SULPHITE  PROCESS.  205 

in  keeping  the  tower  clear.  The  simplest  arrangement  of  all  con- 
sists merely  of  a  spreading-stone  placed  under  the  pipe  from  which 
water  is  delivered. 

Fig.  31  shows  in  a  diagrammatic  way 
one  form  of  the  Mitscherlich  tower  and 
accompanying  draft  tubes.  The  tower 
is  built  of  wood  and  varies  in  height 
from  100  to  135  feet,  and  in  diameter 
from  3  to  5  feet.  The  dimensions  of 
the  one  from  which  our  figure  is  taken  FIG.  30. 

were :  Height,  32  metres  over  all ;  height 

of  absorption  space,  26  metres ;  length  on  each  side  of  tower,  1.2 
metres.  Several  of  such  towers  are  usually  built  together,  the  whole 
being  surrounded  by  a  scaffolding  by  which  access  is  gained  to  the 
top.  As  most  commonly  constructed,  the  towers  have  only  a  single 
false  bottom.  The  construction  shown  in  Fig.  31,  in  which  the 
vertical  shaft  is  divided  into  numerous  compartments  by  a  number 
of  false  bottoms,  is  on  many  accounts  preferable ;  but  such  towers 
hold  less  stone  and  are  more  difficult  to  fill  and  clean.  In  either 
event  the  tower  is  filled  with  limestone  either  from  the  top  or 
through  the  openings  marked  k.  At  the  top  of  the  tower  is  a  tank 
holding  a  considerable  supply  of  water  and  connected  with  a 
sprinkler  just  below  it.  The  valve  controlling  the  supply  of  water 
to  the  sprinkler  is  so  arranged  that  it  can  be  worked  from  the  scaf- 
folding around  the  top  of  the  tower  or  from  the  ground.  There  is 
also  a  pipe  from  the  bottom  of  the  tank  by  which,  when  desired, 
the  whole  body  of  water  can  be  quickly  discharged,  in  order  that 
the  sudden  rush  of-  so  large  a  volume  of  water  down  through  the 
tower  may  carry  along  with  it  the  dirt  and  small  stones  which 
gradually  collect  there  and  at  the  same  time  wash  out  much  of  the 
sulphate  that  has  accumulated.  The  leg  of  the  draft  pipe  nearest 
the  tower  is  often  made  of  glazed  earthenware  pipe,  while  the  leg 
away  from  the  tower  is  built  up  of  sections  of  iron  pipe.  Contrary 
to  the  general  opinion,  these  towers  do  not  act  like  chimneys,  for  the 
escaping  gases  are  often  not  only  heavier  but  colder  than  the  out- 
side air.  The  proper  explanation  of  the  means  by  which  the  draft 
is  maintained  is  this :  the  specific  gravity  of  sulphurous  acid  com- 
pared to  air  is  2.25,  while  that  of  carbonic  acid  is  1.53.  The  gases 
coming  from  the  burners  consist  of  sulphurous  acid  mixed  with 
more  or  less  oxygen  and  sulphuric  anhydride  and  with  a  large  vol- 


206 


THE  CHEMISTRY   OF  PAPER-MAKING. 


ume  of  nitrogen,  and  by  the  time  they  reach  tube  B  they  are  all 
well  cooled.  As  result  of  the  reactions  which  take  place  within  the 
tower,  the  sulphurous  acid  and  sulphuric  anhydride  are  absorbed, 
the  former  being  replaced  by  about  half  its  volume  of  carbonic 


-  26m 


FIG.  31. — DIAGRAM  OF  DIVIDED  MITSCHERLICH  TOWER. 

EXPLANATION  OF  TERMS.  —  Gasrohr,  Gas-pipe ;  Stoakwerk,  Story ; 
Abftuss.  Outlet.    Dimensions  are  in  metres. 

acid,  and  the  latter  by -its  equivalent  of  that  gas.  In  spite  there- 
fore of  the  greater  height  of  the  tower,  the  column  of  gas  within 
it  weighs  less  than  the  shorter  column  of  gas  in  tube  B,  so  that 
there  is  a  constant  upward  flow  and  escape  of  gas  from  the  top  of 


THE  SULPHITE  PROCESS.  207 

the  tower.  That  the  gases  in  the  tower  are  under  this  slight  press- 
ure may  be  shown  by  boring  into  the  tower  at  any  point  when  the 
draft,  instead  of  being  inward,  as  is  the  case  with  the  chimney,  is 
from  within  outward.  It  is  necessary,  however,  in  order  to  secure 
this  draft,  that  the  tube  B  should  have  a  length  of  at  least  153 
inches  for  every  225  inches  in  the  height  of  the  tower,  and  by 
increasing  the  length  of  B  over  that  called  for  by  this  proportion 
the  force  of  the  draft  may  be  augmented  to  any  necessary  extent. 
The  fall  of  the  heavy  column  of  comparatively  cold  gas  in  B  draws 
over  continually  a  fresh  supply  of  hot,  and  therefore  lighter,  gas 
from  the  burners. 

A  number  of  difficulties  is  likely  to  arise  in  working  towers. 
It  is  hard  to  secure  always  an  even  distribution  of  the  water  as  it 
falls  through  the  tower,  and  similarly  to  properly  spread  the  gas  as 
it  passes  upward.  Gutters  are  very  likely  to  form  through  cutting 
away  of  the  stone  at  one  point  more  than  another,  and  any  such 
tendency  increases  rapidly  after  the  first  appearance  of  the  hole. 
The  stone  is  usually  thrown  into  the  tower  from  the  top,  but  in  the 
process  of  working  the  lower  lumps  of  stone  are  continually  eaten 
away,  and  being  pressed  upon  by  the  stone  above  may  pack  together 
and  clog  the  tower  as  the  upper  stone  falls  down.  If  the  stone 
becomes  wedged  at  any  point  in  the  tower,  arches  are  likely  to 
form,  and,  as  the  stone  below  is  eaten  away,  an  open  space  of  con- 
siderable size  may  result.  Finally  the  arch  breaks,  and  the  stone 
above,  settling  suddenly,  may  so  pack  together  as  to  impede  the 
draft.  Such  arches  may  usually  be  broken  before  they  cause 
serious  trouble  by  blows  from  a  heavy  mallet  against  the  outside  of 
the  tower.  Their  existence  is  made  evident  by  the  hollow  sound 
given  out  when  suspected  portions  of  the  tower  are  similarly 
struck,  but  this  involves  so  much  labor  as  to  be  hardly  practicable. 
The  last  traces  of  gas  are  almost  never  absorbed  in  the  tower,  and 
the  unabsorbed  portion  is  frequently  so  considerable  as  to  cause  a 
high  percentage  of  loss.  Crusts  of  monosulphite  and  sulphate  of 
lime  not  unfrequently  become  so  extensive  as  to  impede  or  almost 
stop  entirely  the  flow  of  gas.  Crusts  of  monosulphite  are  espe- 
cially likely  to  form  if  the  gas  is  weak  or  if  the  supply  of  water  is 
curtailed.  For  these  reasons  it  is  necessary  to  inspect  the  condi- 
tion of  the  stone  at  frequent  intervals,  and  to  either  loosen  it  up  by 
a  crowbar,  or  to  remove  it  altogether  and  refill  the  tower  with  fresh 
stone.  The  old  stone  is  piled  up  in  the  air  and  allowed  to  weather, 


208 


THE  CHEMISTRY  OF  PAPER-MAKING. 


in  order  to  cause  the  incrustation  to  loosen  and  flake  off.  These 
difficulties  may  be  avoided  in  large  part  by  making  the  tower 
somewhat  conical  in  shape,  so  that  the  stone  in  working  down 
comes  into  a  wider  and  wider  space. 

The  strength  and  quality  of  the  liquor  made  in  towers  depend 
upon  the  amount  and  strength  of  the  gas  passing  into  the  tower, 
the  quantity  and  temperature  of  water  with  which  the  tower  is 
supplied,  and  the  amount  and  condition  of  the  limestone.  The 
composition  of  the  gas  and  liquor  at  different  heights  in  the  tower 
has  been  studied  by  Harpf,  to  whom  we  are  indebted  for  the  fol- 
lowing table.  The  tower  from  which  the  samples  were  taken  was 
divided,  as  shown  in  Fig.  31,  into  twelve  sections  by  false  bottoms, 
ten  of  the  sections  containing  limestone.  The  percentage  by 
volume  of  sulphurous  acid  in  the  gas  at  the  different  stories  on  two 
different  days  is  shown  below :  — 


Percentage  of  SO2  by  Volume. 

Remarks. 

On  Oct.  17, 

1888. 

On  Oct.  19, 
1888. 

Draft  tube  at  /  . 

about  6.54 

8.92 

First  story  .... 

-- 

— 

Second  story  .     .     . 

4.62 

7.52 

Beginning  of  the  absorption  space. 

Third  story     .     .     . 

3.42 

7.42 

Fourth  story  .     .     . 

2.77 

6.25 

Fifth  story  .... 

2.31 

6.96  (?) 

Sixth  story     .    .    . 

1.95 

5.83 

Seventh  story  .     .    , 

1.57 

5.13 

Eighth  story  .     .     . 

0.92 

3.78 

Ninth  story     .     .    . 

— 

2.29 

Tenth  story    .     .     . 

— 

1.29 

Eleventh  story    .    . 

»*» 

1.16 

Exit  for  gases. 

Twelfth  story  .    .     . 

—  * 

— 

Water  reservoir. 

It  will  be  noticed  that  there  is  a  continual  and  quite  regular 
decrease  in  the  percentage  of  sulphurous  acid  toward  the  top  of 
the  tower.  No  tests  were  made  at  the  first  story,  as  the  liquor 
fell  through  this  to  the  outlet.  The  tests  of  the  17th  were  made 
from  below  upwards,  and  had  to  be  discontinued  at  the  ninth  story, 
as  it  had  become  dark.  The  tests  of  the  19th  were  made  in  the 
forenoon  in  the  reverse  order,  or  l>y  starting  at  the  top  and  work- 
ing down.  The  figure  obtained  at  the  fifth  story  is  probably 
erroneous.  At  the  eleventh  story  the  gas  escaped  into  the  air,  and 


THE  SULPHITE  PKOCE88. 


209 


it  will  be  seen  that  there  was  then  present  1.16  per  cent,  of  SO2,  or 
about  18  per  cent,  of  the  amount  originally  present.  This  of  course 
was  lost.  The  gas  is  cooled  in  its  ascent,  so  that  the  absolute 
volumes  change,  but  each  volume  of  SO2  absorbed  sets  free  an 
equal  volume  of  CO2,  so  that  the  proportions  of  SO2  in  the  total 
volume  at  the  different  points  are  directly  comparable. 

The  composition  of  the  gas  and  liquor  at  the  different  stories  oa 
another  day  is  given  in  the  results  of  the 

EXPERIMENTS  OF  OCTOBER  23,  1888. 


Percentage 
8O2  in 
gases  (by 
volume). 

Percentage  of  SO,  in  liquor 
(by  weight). 

Remarks. 

Total. 

Free.' 

Combined.1 

Draft  tube  .... 

7.70 

„-  . 

__ 



First  story  .... 

— 

^~ 

— 

.  — 

Second  story    .    .     . 

7.28 

3.056 

2.608 

0.448 

Third  story      .     .    . 

8.19  (?) 

2.662 

2,208 

0.454 

Fourth  story    .     .    . 

7.90  (P) 

2.848 

1.984 

0.864 

Fifth  story  .... 

6.32 

3.908 

2.688 

1.280 

(?) 

Sixth  story  .... 

JL48(?) 

1.344 

0.832 

0.512 

Seventh  story  .    .     . 

5.59 

1.488 

0.784 

0.704 

Eighth  story    .    .     . 

4.36 

0.672 

0.426 

0.246 

Ninth  story  .... 

2.58 

0.304 

0.192 

0.112 

Tenth  story     .    .    .r  ; 

1.90 

0.082 

0.049 

0.033 

(?) 

Eleventh  story      .    . 

1.27 

0.520 

0.520 

— 

Gas  exit. 

Twelfth  story  .     .     . 

— 

— 

— 

—  • 

Water  reservoir. 

It  should  be  noted  in  connection  with  these  tables  that  in  Ger- 
many the  sulphurous  acid  present  as  sulphite  of  lime,  CaSO3  is 
called  "  combined  acid,"  while  the  entire  excess  over  that  amount 
is  spoken  of  as  "  free  acid."  This  nomenclature  has  been  followed  in 
these  tables,  although  in  this  country  all  the  acid  present  as  bisul- 
phite of  lime  is  called  "combined  acid,"  while  the  term  "free  acid" 
is  limited  to  the  amount  present  in  excess  of  that  needed  to  form 
bisulphite.  The  German  "free  acid"  might,  perhaps,  better  be 
called  "available  acid,"  since  it  is  the  only  portion  which  is  effec- 
tive in  the  process. 

An  examination  of  the  table  brings  out  the  fact  that  the  liquor 
in  the  eleventh  story  consisted  merely  of  a  solution  of  the  gas  in 
water  which  forms  the  true  sulphurous  acid,  H2SO3 .  In  the  gas 
1  See  remarks  in  text  immediately  following  table. 


210  THE  C&EMI8TRY  OF  PAPER-MAKING. 

analyses  the  figures  at  the  third*  fourth,  and  sixth  stories  do  not 
show  the  expected  decrease  in  the  percentage  of  SO2  by  volume. 
Tliis  may  have  been  due  to  inequalities  in  the  gas  caused  by  irreg- 
ular work  at  the  burners.  It  will  also  be  noted  that  the  liquor 
from  the  fifth  story  is  stronger  than  any  taken  lower  down.  Harpf 
considers  that  the  difference  here  found  is  a  real  one,  due  to  the  fact 
that  the  lower  stories  contained  comparatively  little  limestone,  and 
that  there  was  sufficient  oxidation  to  reduce  the.  strength  of  the 
liquor.  We  have  frequently  observed  a  similar  loss  of  strength  in 
case  of  finished  liquors  which  were  exposed  for  a  time  to  the  fur- 
ther action  of  the  gas.  In  the  present  case,  however,  as  Harpf  stig- 
gests,  the  discrepancy  may  have  been  due  simply  to  guttering. 

The  tower  upon  which  these  experiments  were  made  was  supplied 
with  gas  from  pyrites  burners,  and  in  other  tables  given  by  Harpf 
the  proportion  of  SO*  present  in  the  burner  gas  by  volume  ranges 
from  2.30  to  18.80  per  cent.  The  average  figure  is  about  7.5  per 
cent. 

Before  taking  these  samples  the  liquor  flowing  from  the  tower 
stood  6°.  Be",  and  contained  — 

Per  cent. 

Free  sulphurous  acid .    .    .    3.232 

Combined  sulplrffrous  acid  .    .    .    .,'    .    .     .    0.768 

Total 4.000 

while  at  the  conclusion  of  the  tests'  it  stood  6|°  Be*,  and  coiv 
tainsd — 

Per  cent. 

Free  sulphurous  acid  .     .     .     .     .     .     .     .     .     2.944 

Combined  sulphurous  acid  .     .     .     .    ....     0.896 

Total       ..    .     .     .    *    .    ...   .    .     .     .     3.840 

Ekman,  as  already  stated,  at  first  prepared  the  solution  of  bi- 
sulphite of  magnesia  used  in  his  process  irr  small  towers  about 
5  feet  in  diameter  and  14  feet  high.  These  were  filled  with  cal- 
cined magnesia,  but  as  this  material  even  in  large  lumps  rap- 
idliy  softens  up  and  becomes  pasty  under  the  action  of  the  water, 
while,  moreover,  it  is  impossible  to  calcine  the  magnesite  without 
producing  a  large  proportion  of  material  too  fine  to  be  used  in  a 
tower,  he  was  compelled  to  abandon  them  and  adopt  a  modified 
tower  working  upon  quite  a  different  principle.  This  tower  is 
built  of  heavy  sheet  lead,  supported  by  a  stout  framework  of  tim- 


THE  'SULPHITE  PROCESS. 


211 


her,  and  is  about  20  feet  square  by  60  feet  in  height.     It  is  filled 
above  the  false  bottom  with  flints,  and  milk  of  magnesia  instead  of 


FIG.  32.  —  RiTTEB-KELwrER  TANK  APPARATUS. 

water  is  delivered  at  the  top  in  an  intermittent  stream.     Tills  is 
spread  in  thin  films  over  the  surface  of  the  flints  and  rapidly  absorbs 


212 


THE  CHEMISTRY  OF  PAPER-MAKING. 


the  gas,  with  the  formation  first  of  monosulphite  and  then  of  bisul- 
phate  of  magnesia.  The  chemical  reactions  in  a  tower  of  this  form 
are  essentially  the  same  as  those  occurring  in  the  common  form  of 
tank  apparatus.  As  with  other  forms  of  towers,  there  is  a  consider- 
able escape  of  sulphurous  acid  from  the  top. 

Fig.  32  shows  a  form  of  liquor  apparatus  which  has  been  patented 
and  worked  by  Hitter  and  Kellner,  and  which  combines  in  consid- 
erable measure  the  features  of  both  towers  and  tanks.  The  por- 
tion of  the  apparatus  in  which  the  liquor  is  made  consists  of  a  set 
of  four  closed  tanks,  (7,  D>  E,  F^  each  provided  with  a  perforated 


\>X^\\X\V^XV^^ 

FIG.  33.  —  MCDOUOALL  LIQUOR  APPARATUS. 

false  bottom  upon  which  rests  the  limestone  with  which  the  tank 
is  about  three-quarters  filled.  The  tanks  are  filled  with  water  to  a 
point  just  above  the  limestone.  The  gas  from  the  burners  after 
passing  through  the  purifier  A  and  cooler  is  drawn  by  the  gas 
pump  G-  up  through-  the  tanks  C  and  D  in  succession,  being  first 
delivered  through  the  perforated  pipe  coiled  beneath  the  false  bot- 
tom of  tank  (7,  and  bubbling  up  through  the  water  on  its  way  to 
tank  D,  up  through  which  it  similarly  passes.  As  the  gas  is  being 
continually  sucked  away  from  D  by  the  pump,  both  C  and  D  are 
working  under  a  partial  vacuum.  The  gas  which  has  been  drawn 
from  D  is  then  forced  by  the  pump  into  tank  E  below  the  false 


THE  SULPHITE  PROCESS. 


213 


bottom,  and  as  it  passes  up\vard  into  pipe  5  it  is  similarly  forced 
along  through  F.  By  this  time  all  the  sulphurous  acid  has  been 
absorbed  and  the  waste  gases  escape  from  I*  through  the  pipe  Cr. 
As  the  liquor-making  progresses  fresh  water  is  from  time  to  time 
run  in  through  a  pipe  in  the  top  of  F,  from  which  tank  it  can  be 
transferred  into  E  as  needed,  through  the  pipe  h.  On  account  of 
the  pressure  in  tank  E  the  liquor  in  E  can  be  transferred  to  D 
whenever  the  valve  in  the  pipe  *  is  open,  and  from  D  may  be  run 
into  (7,  which  like  D  is  under  a  partial  vacuum. 


y////y///////////////^^^^^ 

FIG.  33.  —  McDouoALL  LIQUOR  APPARATUS. 

The  chemical  reactions  taking  place  in  the  tanks  are  similar  to 
those  which  take  place  at  what  may  be  called  the  corresponding 
stories  in  the  tower.  The  gas  is  first  absorbed  by  the  water,  to  form 
a  solution  of  sulphurous  acid,  which  reacts  upon  the  limestone,  set- 
ting free  carbonic  acid  and  forming  in  the  first  case  sulphite  of  lime. 
The  gas  passing  along  through  the  tanks  in  series  gradually  loses 
all,  or  nearly  all,  its  sulphurous  acid  and  becomes  more  and  more 
highly  charged  with  the  carbonic  acid  which  passes  away  with  the 
waste  nitrogen.  After  a  time,  as  the  water  takes  up  sufficient  gas, 
the  sulphite  is  dissolved  with  the  formation  of  bisulphite,  and  when 


214  THE  CHEMISTRY  OF  PAPER-MAKING. 

the  liquor  in  tank  C  has  reached  the  desired  strength  it  is  drawn  off 
and  replaced  by  weak  liquor  f  roni  the  tank  next  in  series,  the  others 
being  similarly  emptied  and  filled,  until  the  last  tank  is  charged 
again  with  fresh  water.  ^ •••> 

This  apparatus  has  not,  so  far  as  we  know,  come  into  use  in.  this 
country.  The  novel  form  of  cooler  to  which  reference  was  made  on 
page  203  should  be  noticed.  Its  construction  is  clearly  shown  in 
plan  and  section  in  Fig.  2,  The  cooling  surface  is  greatly  increased 
by  numerous  cross  tubes  in  the  cooling-pipes,  as  shown  at  b*  in  Fig. 
3.  These  cross  tubes  are  open  at  the  ends  so  that  the  water  passes 
through  them.  Figs.  2  and  3  are  sub-figures  in  Fig.  32. 

The  apparatus  patented  by  McDougall  and  used  with  some  mod- 
ification by  Partington  is  shown  in  Fig.  33,  and  either  in  this  or 
its  modified  arrangement  is  the  type  which  has  been  most  generally 
introduced  in  this  country.  As  used  by  McDougall  it  consists  of 
three  tight  tanks  fitted  with  agitators  and  with  pipes  by  which  the 
gas  coming  from  the  furnace  is  discharged  near  the  bottom  of  the 
first  tank  and  is  carried  onward  through  the  series,  as  indicated  by 
the  arrows.  The  tanks  are  nearly  filled  with  milk  of  lime,  which 
may  be  transferred  from  one  tank  to  the  other  through  the  pipes  S. 
Cr  Q-  on  each  tank  are  gauges  with  glass  tubes,  in  which  the  level 
of  the  liquid  in  the  tanks  may  be  seen.  The  sulphur  is  burned  in 
the  retort  under  a  pressure  of  8  to  5  Ibs.,  which  is  maintained  by 
an  air  compressor,  and  the  gas  passes  through  a  series  of  water- 
jacketed  cooling-pipes  before  passing  into  the  first  tank.  All  the 
tanks  are  first  charged  with  milk  of  lime,  and  as  soon  as  the  liquor 
in  vat  No.  1  comes  to  test  it  is  drawn  off  into  settling-tanks ;  the 
valves  between  the  absorbing-tanks  are  then  opened,  and  fresh  milk 
of  lime  is  run  into  the  last  tank  until  the  level  of  liquor  in  all 
three  is  again  brought  to  the  proper  point. 

Although  a  somewhat  better  absorption  of  gas  is  secured,  several 
disadvantages  present  themselves  when  sulphur  is  thus  burned 
under  pressure.  A  great  amount  of  steam  is  required  for  the  air 
compressor,  and  there  is  difficulty  in  keeping  the  tanks  tight. 
Rather  more  sulphur  is  burned",  and  the  danger  of  sublimation  and 
formation  of  polythionic  acids  from  overheating  is  considerably 
increased.  The  proportion  of  SO3  formed  is  also  greater  than 
where  the  combustion  proceeds  slowly  under  the  normal  or  slightly 
diminished  pressure.  In  a  retort  working  under  pressure  about 
3  Ibs.  of  sulphur .  are  burned  per  hour  per  square  foot  of  pan 
surface. 


THE  SULPHITE  PROCESS. 


215 


In  the  Partington  apparatus,  Fig.  34,  similar  tanks  are  used,  but 
they  are  placed  one  above  the  other  and  the  gas  is  drawn  through 
them  by  a  pump  connected  to  the  pipe  by  which  the  waste  gases 
leave  the  highest  tank.  As  used  by  Partington,  there  is  a  con- 
tinuous flow  of  liquor  through  the  apparatus,  fresh  milk  of  lime 
running  constantly  in  a  carefully  regulated  stream  into  the  upper 


GAS 


KAN 

FIG.  34. — PARTINGTON  .LIQUOR  APPARATUS. 

tank,  while  a  corresponding  amount  of  finished  liquor  overflows 
from  the  lowest  tank  nearest  the  furnaces.  In  the  United  States 
the  discharge  of  liquor  -from  this  apparatus  has  generally  been 
intermittent,  the  ohargeiin  the  bottom  tank  being  brought  to  test 
and  drawn  off  before  the  charges  in  the  other  tanks  are  transferred, 
and  fresh'  milk  of  lime  run  into  the  upper  tank. 

The  liquor  apparatus  employed  by  Wheelwright  overcomes  the 


216 


THE  CHEMISTRY  OF  PAPER-MAKING. 


difficulties  encountered  when  the  gas  is  forced  through  a  consider- 
able column  of  liquid,  and  is  so  constructed  that  the  gas  has  a  free 
passage  over  the  surface  of  the  liquor,  which  is  exposed  to  its 
action  in  thin  films.  It  permits  the  use  of  an  ordinary  fan  blower 
in  place  of  the  much  more  expensive  gas  pump,  and  there  is  con- 
sequently a  considerable  saving  of  power.  The  apparatus  consists 
of  three  horizontal  cylinders  built  of  3-inch  Southern  pine  staves* 


FIG.  35. — McDouc ALL'S  LATER  APPAKATUS. 

and  placed  one  above  the  other.  The  cylinders  are  usually  about 
20  feet  in  length,  and  either  5  or  6  feet  in  diameter.  Short  and 
heavy  bronze  shafts  ending  inside  the  tanks  in  a  head,  to  which 
the  heavy  wooden  shaft  is  secured,  pass  through  stuffing-boxes 
secured  to  each  head  of  the  tank.  To  the  wooden  shaft  is  attached 
a  system  of  paddles,  arranged  like  those  on  a  stern-wheel  steamer. 
The  tanks  are  filled  with  milk  of  lime  or  magnesia  up  to  the  level 
of  the  shaft.  The  gas  enters  the  bottom  tank  above  the  surface  of 
the  liquor,  and  passes  along  over  it  through  the  three  tanks  in 
succession,  The  shaft  revolves  about  eighteen  times  a  minut^, 
and  as  each  paddle  comes  out  of  the  liquor  the  latter  is  exposed  to 
the  gas,  partly  as  spray  and  partly  as  the  thin  film  adhering  to  the 
paddle.  The  conditions  for  absorption  are  so  favorable  that  the 


THE  SULPHITE  PROCESS. 


217 


capacity  of  this  apparatus  is  practically  limited  only  by  the  amount 
of  sulphurous  acid  gas  passed  through  it.  With  the  proper  num- 
ber of  sulphur  furnaces,  2500  gallons  or  more  of  liquor,  standing 
6°  Be*.,  may  be  obtained  per  hour.  The  only  difficulty  which  is 
likely  to  be  experienced  is  due  to  the  tendency  of  the  monosulphite 
of  linie  to  crystallize  upon  the  paddles  in  the  second  cylinder.  As 
patented  by  Catlin  the  apparatus  is  discharged  intermittently. 

The  second  and  later  form  of  liquor  plant  employed  by  Mc- 
Dougall  is  shown  in  plan  in  Fig.  35,  and  is  in  principle  essentially 
the  same  as  the  apparatus  just  described.  The  cylinders  marked  A 
are  arranged  so  that  they  may  be  rotated  by  worm  and  gear ;  Az  is 
a  stationary  tank  of  the  ordinary  form,  with  an  air-tight  cover  and 
agitator.  Attached  to  the  interior  of  the  vessel  A  are  projections, 
a,  intercepted  by  transverse  partitions,  a2,  with  central  apertures,  a3, 
to  allow  of  the  passage  of  the  gas  and  liquid  through  the  vessel. 
These  projections  as  they  move  carry  with  them  a  portion  of  the 
liquid  and  shower  it  upon  the  gas,  whilst  the  transverse  partitions 
prevent  an  immediate  flow  of  the  liquid  from  one  end  to  the  other. 
The  level  of  the  liquid  is  such  as  to  leave  a  passage  for  the  gas 
over  its  surface.  D  are  connecting  pipes  for  the  passage  of  the 
gas  and  liquid  from  vessel  to  vessel.  The  milk  of  lime  is  stored  in 
the  tank  Z)2,  and  its  flow  is  regu- 
lated by  a  tap.  A  continuous  cur- 
rent of  sulphurous  acid  gas  enters 
the  apparatus  at  E,  and  meets 
successively  a  shower  of  liquid  in 
the  rotating  vessels,  while  much 
of  the  liquid  is  also  exposed  to 
its  action  as  a  film  upon  the  par- 
titions. The  gas  and  liquid  move 
in  opposite  directions,  the  course 
of  the  gas  being  shown  by  the 
dotted  arrows  and  that  of  the 
liquid  by  the  full  arrows.  This 
apparatus  is  evidently  well 
adapted  to  secure  a  rapid  and  FlG  ^ 

complete  absorption  of  gas.   We 

have  not  seen  it  in  operation,  but  it  must  be  difficult  to  clean,  and, 
except  in  the  tank  next  to  the  furnace,  troublesome  crtfsts  of  mono 
sulphite  must  be  likely  to  form  upon  the  partitions  and  projections. 


218 


THE  CHEMISTRY  OF  PAPER-MAKING. 


FIG  .  37.  —  RiTTBit-Kmtanni 


The  apparatus  shown  in  Fig.  86  is  described  in  the  French 
patent  No.  157,754,  quoted  by  Hoyer  and  Schubert.  A  is  a  water 
tank,  D  a  tank  partly  filled  with  limestone,  and  C  is  another  reser- 
voir for  water.  The  fur- 
nace gases  are  drawn  along 
the  pipe,  JK,  by  the  action 
of  the  injector,  B>  which 
works  by  water  from  the 
tank,  A.  The  descending 
water  carries  the  gas  down 
to  D,  where  it  passes  up 
through  the  liquor  in  which 
the  limestone  is  submerged, 
and  escapes  through  11'  and 
Rn  into  (7,  where  it  bubbles 
through  the  water  therein 
contained  before  making  its 
final  exit.  A  portion  of  .the  waste  gases  is,  however,  drawn  back 
by  B  and  sent  around  again.  The  pump,  JP,  keeps  the  liquor  in 
circulation  by  drawing  .firan  D  .and  discharging  into  A.  The  con- 
tents of  C  are,  when 
necessary,  trans- 
ferred to  J.,  after 
which  C  is  again 
filled  with  fresh 
water. 

Frank  has  em- 
ployed a  tower 
which  is,  in  its  gen- 
eral principles,  sim- 
ilar to  that  of 
Mitscherlich.  The 
apparatus  at  first 
brought  out  by 
Ritter  and  Kellner 
consistsflof  five  tow- 
ers of  .moderate 


FIG.  38.  —  RITTER-KELLNER  TOWJSRS. 


height,  shown  in  sectional  elevation  in  Figs.  37,  38,  and  in  plan  in 
Fig.  39.  In  connection  with  the  towers  there  is  sometimes  worked 
a  set  of  tight  boxes  filled  with  lumps  of  limestone,  and  shown  at 


THE  SULPHITE  PROCESS. 


219 


Q  in  Fig.  40.  A  second  set  of  boxes  is  shown  at  R,  and  these  may 
be  filled  with  the  carbonate  of  another  base,  as  niagnesite.  The 
gas  enters  under  the  false  bottom  of  tower  .#,  and,  after  passing  up 
through  the  limestone 
in  the  tower,  is  carried 
along  by  a  pipe  to  the 
bottom  of  the  next  tower, 
and  so  on  through  the 
series.  The  tower,  jF,  is 
supplied  with  fresh  wa- 
ter, and  the  weak  liquor 
flowing  from  this  tower 
is  pumped  up  and  sent 
through  J?,  />,  and  O  in 
succession.  It  is  at  this 
stage  charged  with  con- 
siderable free  acid,  and 
is  sent  through  the  boxes 
Q,  where  it  takes  up  an 
additional  quantity  of 
lime..  From  Q  it  is  sent 
through  J5,  where  it 
meets  the  strong  gas, 
and  after  leaving  this  tower  it  is  sent  through  the  second  set  of 
boxes,  72,  to  take  up  the  desired  quantity  of  the  second  base. 
When  it  is  desired  to  obtain  a  liquor  carrying  a  greater  proportion 
of  gas  to  base  than  is  secured  when  limestone  is  used  in  the  towers, 
certain  or  all  of  them  may  be  tilled  with  coke  or  some  substance 
which  is  not  acted  upon  by  the  solution/ 

The  Ritter-Kellner  towers  ar&.in  this  country  built  of  wood,  and 
are  commonly  5  feet  in  diameter  and  about  25  feet  high.     The  use 

of  the  boxes,  ft  and  of  coke  in 
any  of  the  towers  has,  w&  believe, 
been  generally  discontinued  as  in- 
troducing unnecessary  complica- 
tion.. As  at  present  worked,  the 
group  of  five  towers  may  be  re- 
garded as  a  single  Mitscherlich  tower,  built  in  sections  which  are 
placed,  for  convenience,  on  the  same  level.  The  difficulties  in 
working  them  are  similar  in  kind  though  rather  less  in  degree  to 
t)\ose  encountered  with  the  Mitscherlich  tower. 


FlG.  39. RlTTEK-KfiLLNEK    TOWERS. PLAN. 


FIG.  40. 


220 


THE  CHEMISTRY  OF  PAPER-MAKING. 


The  Ne"methy  liquor  apparatus,  which  is  shown  in  plan  and  in 
sectional  elevation  in  Fig;  41,  is  similar  in  principle  to  the  Kell- 
ner  apparatus  just  described,  but  is  rather  simpler  in  detail.  The 
four  towers,  B,  are  packed  with  limestone,  as  are  also  the  two 


'— r~r-~  —  .iT— "A   ~~-     -  ""  — ~  — ~~=- 
'—     -     — '-    -./I      —~~---.——^ 


Fio.  41. —  THE  NEMETHY  LIQUOR  APPARATUS, 

tanks,  C.  The  gas  enters  the  system  at  0,,  and  passes,  as  will  be 
noticed,  down  the  first  tower.  It  then  enters  the  bottom  of  the 
second  tower,  through  which  it  passes  upward.  From  there  it 
passes  down  the  third  tower,  and  up  the  fourth,  which  it  leaves  at 


THE  SULPMITE  PROCESS. 


221 


02.  Water  enters  through  the  branched  pipe,  H2)  and  is  delivered 
at  the  top  of  the  towers  through  the  sprinklers,  b.  The  liquor 
flowing  from  the  towers  enters  the  bottom  of  the  limestone  tanks 
through  the  pipe  TI  .  Here  any  excess  of  SO2  reacts  upon  the  lime- 
stone, while  the  sulphate  of  lime  settles  out  as  the  liquor  slowly 
rises.  The  clear  liquor 
runs  off  through  r2  into 
the  storage  tank,  A. 
By  means  of  the  pump, 
P,  the  liquor,  if  below 
test,  may  be  again 
drawn  from  A  and 
sent  through  the  sys- 
tem. 

The  Wendler-Spiro 
liquor  apparatus  is 
shown  in  Fig.  42,  in 
which  are  the  sub-fig- 
ures 1  and  2.  Only 
the  absorption  appara- 
tus is  here  shown.  The 
complete  plant  com- 
prises also  a  very  large 
cast-iron  retort,  which 
is  kept  submerged  in 
water,  and  in  which 
the  sulphur  is  burned 
under  pressure  ;  an  air- 
pump  ;  a  subliming 
box  or  chamber  for 
holding  back  sulphuric 
acid  and  sublimed  sul- 
phur; and  a  cooler  of 
efficient  form. 


FIG.  42.  —  THE  WENDLER-SPIRO  LIQUOR  APPARATUS. 


Fig.  1  is  a  sectional  view  of  the  apparatus.  Fig.  2  is  a  top  view 
of  the  lower  part  of  the  same,  partly  in  section,  the  letters  A,  B,  <?, 
and  Z>  indicating  the  vats. 

K  is  the  absorption  chamber,  provided  with  drip  shelves  a  a, 
the  vats  and  the  chamber  being  connected  by  a  system  of  pipes. 
The  lime-water  necessary  for  the  liquor  enters  the  vat  D  by  the 


222  THE  CHEMISTRY  OF  PAPER-MAKING. 

pipe  11.  The  sulphurous  acid  enters  the  vats  A,  B  under  pressure 
by  the  pipe  1,  and  passes  either  through  -A,  jRT,  and  D,  or  J5,  JS", 
and  D,  the  lime-water  passing  either  through  D,  K,  and  A,  or  D, 
Jf,  and  B.  The  gas  cannot  be  completely  absorbed  by  the  liquid 
in  the  vats  A,  B,  on  account  of  the  rapidity  with  which  it  passes 
through  it,  and  therefore  the  absorption  chamber  J£,  provided  with 
drip  shelves  a  a,  is  put  in,  which  affords  the  gas  the  largest  possi- 
ble plane  of  attack.  It  is  the  object  to  let  the  weak  liquor,  which 
is  still  able  to  absorb  a  large  quantity  of  sulphurous  acid,  run  as 
often  as  possible  over  the  shelves  in  the  saturating  chamber  /f, 
whereas  the  strongest  liquor,  which  is  unable  to  absorb  much  more 
sulphurous  acid,  is  finally  charged  with  gas  in  the  lower  vats. 
The  incomplete  liquor  passes  from  A  or  B  through  the  pipe  2  to 
(7,  and  from  C  through  K  back  to  A  or  B.  The  liquor  is  com- 
pleted in  either  A  or  J5,  and  then  passes  through  the  pipe  2,  2'  to 
the  place  of  consumption.  The  vat  D  is  used  for  the  reception 
of  lime-water,  and  the  vat  0  for  the  reception  of  the  weaker 
liquor. 

The  system  of  pip:.ng  by  which  the  vats  -4,  B,  6',  Z),  and  the 
chamber  K  are  connected  is  as  follows :  The  gas  is  conducted  to 
the  vats  A,  B  by  the  pipe  1,  and  from  A,  B  to  the  saturating  cham- 
ber K  by  pipes  5  and  6,  from  K  to  the  vats  (7,  D  by  the  pipes  9  and 
10 — the  partial  object  of  10  being  to  allow  the  free  flow  of  the 
liquid  from  the  vat  C  when  the  valve  8  is  opened.  The  liquids  are 
conducted  through  the  pipes  7  and  8  into  K^  from  there  by  the 
pipes  3  and  4  to  A  B,  and  from  these  vats  they  may  be  carried 
to  the  outlet  2'  or  to  the  vat  C  by  the  pipe  2. 

Suppose  the  vats  A  and  B  are  already  filled  with  weak  liquor. 
0  is  empty,  and  D  contains  lime-water.  The  gas  enters  through 
the  pipe  1  into  the  vats  A  and  J5,  and  up  through  the  saturating 
chamber  K  to  J).  The  valves  in  the  pipes  7,  8,  and  9  are  then 
closed,  and  the  valve  &  in  the  pipe  2  is  opened.  Pressure  will 
then  increase  in  A^  B^  and  K  until  it  is  sufficient  to  force  the 
weak  liquor  from  B  to  C.  As  soon  as  this  is  accomplished,  the 
valve  8  is  opened,  and  the  weak  liquor  is  allowed  to  pass  from  € 
over  the  shelves  in  the  saturating  chamber  K,  and  then  through 
the  pipe  4  to  the  vat  B.  On  this  passage  it  will  absorb  the  gas 
which  is  in  K.  The  outflow  of  C  is  regulated  in  such  a  manner 
that  as  soon  as  B  is  nearly  filled  the  liquor  in  A  will  also  nearly 
have  absorbed  the  desired  amount  of  sulphurous  acid. 


THE  SULPHITE  PROCESS.  223 

As  soon  as  this  is  accomplished,  the  gas  is  switched  over  to  J9, 
and  the  outlet  valves  from  ,/Tare  again  closed,  and  the  completed 
liquor  is  forced  over  from  B  to  the  pipe  2  21'  to  the  place  of  con- 
sumption. As,  meanwhile,  chamber  K  is  under  pressure  of  sul- 
phurous acid,  the  lime  which  has  settled  in  chamber  K  will  be 
d  issolved,  and  thus  it  is  possible  to  obtain  a  liquor  containing  an 
equal  percentage  of  lime;  and  also  in  this  manner  the  drip  shelves 
of  the  chamber  IT  will  be  kept  clean,  thus  excluding  the  possibility 
of  an  obstruction  in  the  chamber  K.  When  all  of  the  completed 
liquor  has  been  forced  out  of  the  vat  A  or  B,  fresh  lime-water  will 
be  conducted  into  such  empty  vat'  by  opening  the  valve  in  the 
pipe  7  and  allowing  the  lime-water  to  run  over  the  shelves  a  of  the 
chamber  K  to  the  vat  A  or  /?,  By  closing  the  gas  outlet  valves 
of  K  the  weak  liquor  is  forced  from  A  to  C.  Then  by  opening 
the  valve  8  the  weak  liquor  is  allowed  to  pass  from  C  .over  the 
saturating  shelves  a  a  of  the  chamber  K  to  A.  After  the  same 
liquid  from  one  of  the  lower  vats  —  say  A  —  has  passed  over  the 
saturating  shelves  ia  K  twice,  the  liquor  in  the  other  lower  vat  — 
gay  JS — is  nearly  completed.  The  gas  is  then  switched  over  and 
conducted  through  the  vat  A,  the  outlet  valves  from  If  are  closed, 
and  the  completed  liquor  is  forced  from  B  through  the  pipe  2  2' 
to.  the  place  of  consumption. 

In  this  case  the  apparatus  is  worked  under  gas  pressure;  out 
the  same  effect  would  be  obtained  by  suction.  The  circulation  of 
the  liquids  could  likewise  be  obtained  by  pumping. 

The  Behrend  liquor  apparatus  which  is  commonly  used  in  mills 
working  the  Salomon-Brungger  process  is  very  similar  to  the 
apparatus  of  Weiidler  and  Spiro,  but  lacks  the  absorption  box 
which  adds  greatly  to  the  efficiency  of  the  latter  plant.  The 
Behrend  apparatus  is  in  fact  practically  a  Partington  plant  with- 
out agitators,  agitation  being  secured  by  the  upward  passage  of 
the  gas. 

The  liquor  apparatus  of  Dr.  Frank  is  shown  in  plan  and 
elevation  in  Fig.  43,  for  which  we  are  indebted  to  Schubert's 
"  Cellttlosefabrxkation."  Although  this  apparatus  has  been  in  use 
in  many  continental  mills,  it  has  not,  so  far  as  we  know,  yet 
found  a  place  in  this  country.  It  is,  however,  to  our  minds,  one 
of  the  best  which  has  thus  far  been  devised,  arid  we  take  pleasure 
in  introducing  it  to  the  favorable  consideration  of  American  paper- 
makers. 


224 


THE  CfHEMISTRY  OF  PAPER-MAKING. 


In  the  figures,  A  represents  a  closed  sulphur  oven  in  which 
combustion  is  maintained  by  the  air-pump  B,  which  is  provided 
with  the  air-chamber  (7,  to  equalize  and  regulate  the  pressure. 
The  gas  from  the  furnace  passes  first  into  the  subliinator  D,  in 
which  most  of  the  sulphur  which  may  have  been  carried  over  is 


^^':^'^%2;^/005i%^ 

FIG.  43. — DR.  FRANK'S  LIQUOR  APPARATUS. 

condensed,  the  remainder  being  caught  in  the  dust-chamber  -£'. 
After  passing  through  the  cooler,  the  gas  is  sent  through  the 
small  washing  tank  1,  which  is  partially  filled  with  water,  to  hold 
back  any  sulphuric  acid  which  may  be  present  in  the  gasv  and 
from  this  washer  there  may  be  drawn  from  time  to  time  a  weak 
sulphuric  acid  for  use  about  the  mill.  2,  3,  and  4  are  absorption 
vessels  fitted  with  vertical  agitators,  and  the  gas  passes  through 


THE  SULPHITE  PROCESS.  225 

them  in  the  order  of  their  numbers.  Tanks  2  and  3  are  closed, 
and  work  under  pressure,  but  No.  4  is  generally  open,  and  is  the 
ono  into  which  the  fresh  milk  of  lime  is  charged.  The  milk  of 
lime  is  made  up  very  strong,  and  absorption  goes  on  in  the  last 
two  tanks  until  the  liquor  in  them  is  beyond  the  monosulphide 
stage  and  well  along  toward  bisulphite.  The  charge  in  3  is  then 
transferred  to  2,  being  at  the  same  time  diluted  with  sufficient 
cold  water  to  bring  the  finished  liquor  to  the  proper  boiling 
strength.  It  will  be  noticed  that,  for  this  reason,  tank  2  is  made 
considerably  larger  than  the  others.  There  is,  of  course,  always 
some  heating  up  of  the  liquor  in  the  two  smaller  tanks ;  but  the 
evil  effects  of  this  are  corrected  by  the  admission  of  so  large  a 
volume  of  cold  water,  which  is  in  the  best  condition  for  the  rapid 
absorption  of  gas.  It  ordinarily  requires  only  about  3  minutes 
to  bring  the  monosulphite  in  solution  in  tank  2,  and  finish  off  the 
liquor.  The  air-pump  is  then  stopped,  and  the  combustion  of 
sulphur  ceases  for  the  time.  The  finished  liquor  is  then  drawn 
off,  and  a  fresh  charge  from  3  transferred  to  2,  while  the  tanks  3 
and  4  are  being  refilled  with  fresh  milk  of  lime.  The  charging  and 
emptying  take  about  30  minutes,  and  the  whole  operation  about  7 
hours.  The  capacity  of  the  apparatus  is  from  30  to  35  cubic  metres 
for  the  small  size,  or-frpm  54  to  60  cubic  metres  for  the  large  size, 
for  24  hours.  It  can  be  arranged  to  run  continuously,  but  Dr. 
Frank  prefers  the  intermittent  method,  as  results  may  thus  be 
better  con  trolled. 

In  this  apparatus,  Dr.  Frank  has  used  lime,  magnesia,  and  soda, 
and,  where  desirable,  can  bring  the  test  of  the  liquor  up  to  10°  B. 
The  guarantee  given  with  the  apparatus  is  that  95  per  cent,  of  the 
sulphur  burned  shall  be  brought  into  the  liquor  in  a  form  avail- 
able for  use;  or,  in  other  words,  for  every  100  kilogrammes  of 
sulphur  burned,  there  shall  be  obtained  in  the  liquor,  190  kilo- 
grammes of  sulphurous  acid.  In  practice,  193.6-194  have  been 
obtained. 

Dr.  Frank,  acting  upon  the  theory  that  the  work  of  the  liquor 
is  effected  by  the  free  sulphurous  acid,  advises  the  preparation  and 
use  of  liquor  with  as  small  a  content  of  lime  as  possible.  This  is 
entirely  in  accord  with  our  own  views,  and  the  point  is  one  which 
deserves  much  more  careful  attention  from  pulp-makers  than  it 
has  yet  received.  It  should  be  borne  in  mind  that  by  "  free  acid  " 
Dr.  Frank  has  reference  to  all  the  gas  present  in  the  liquor  in 


226  THE  CHEMISTRY  OF  PAPER-MAKING. 


excess   of   that    required    to   form   monosulphite   with    the   base 
present. 

In  discussing  the  working  of  his  apparatus,  Dr.  Frank  offers  the 
following  as  an  example  of  an  ordinary  factory  liquor  of  7°  Be, 
and  made  in  an  apparatus  other  than  his  own  :  — 

Sample  A. 

Per  cent. 

Free  sulphurous  acid    .  . 2.35 

Combined  sulphurous  acid 2.00 

Total 4.35 

Lime 1.75 

For  comparison  with  this,  he  submits  a  liquor  of  barely  5°  Be, 
made  in  his  apparatus,  and  which  pulped  the  wood  in  the  same 
length  of  time  as  above,  without  any  separation  of  sulphite.  The 
composition  of  the  liquor  was  as  follows :  — 

Sample  B. 

Per  cent. 

Free  sulphurous  acid 2.382 

Combined  sulphurous  acid      .....  0.874 

Total 3.256 

Lime  .    /   .  v.    V 0.764 

It  will  be  noticed  that  this  liquor,  although  of  less  specific 
gravity,  and  containing  a  smaller  total  of  sulphurous  acid,  is 
nevertheless  richer  in  available  acid  than  A.  Sample  A  required 
23  kilogrammes  of  sulphur  per  cubic  metre,  while  B  required  only 
17  kilogrammes.  The  ash  of  the  pulp  cooked  with  A  was  1.85 
per  cent.,  while  that  from  the  pulp  cooked  with  B  was  only 
0.36  per  cent. 

A  liquor  used  at  the  Krumauer  Fabrik,  working  under  the 
Mitscherlich  system,  had  the  composition  shown  below :  — 

Per  cent. 

Free  sulphurous  acid '  .     .     2.023 

Combined  sulphurous  acid 1.012 

Total .     3.035 

Lime 0.827 

and  required  only  16  kilogrammes  of  sulphur  for  a  cubic  metre. 
In  spite  of  the  fact  that  less  sulphur  was  used* to  make  this  liquor, 


THE  SULPHITE  PROCESS.  227 

it  is  a  more  expensive  liquor  than  .8,  which  took  17  kilogrammes, 
because  the  proportion  of  free  acid  in  B  is  so  much  greater  that 
B  is  the  more  efficient  liquor,  and  can  therefore  be  used  in  less 
amount. 

In  these  different  forms  of  apparatus  in  which  milk  of  lime  is 
used,  it  is  perhaps  somewhat  less  trouble  to  work  them  in  the 
continuous  way,  but  the  quality  of  the  liquor  is  more  easily  con- 
trolled when  the  liquor  is  carried  through  in  separate  charges. 
Each  charge  can  then  be  tested  for  strength,  and  dumped  as  soon 
as  it  comes  to  test.  It  is  important  that  the  finished  liquor  should 
be  removed  from  the  absorption  tank  as  soon  as  possible,  as  other- 
wise it  is  liable  to  be  weakened  through  the  formation  of  sulphuric 
acid.  It  is  easier  to  settle  out  the  last  portions  of  monosulphite 
than  to  try  to  bring  them  into  solution,  and  considerable  time 
may  thus  be  saved.  Besides,  the  greater  portion  of  the  iron  which 
was  present  in  the  lime  does  not  go  into  solution  until  nearly  all 
the  sulphite  is  dissolved,  and  there  is  less  danger  from  contamina- 
tion from  this  source  when  the  liquor  is  drawn  off  before  it  is 
entirely  clear. 

The  quality  of  the  lime  used  in  the  preparation  of  these  liquors 
is  of  the  first  importance,  and  its  value  for  this  purpose  increases 
with  the  amount  of  magnesia  it  contains. 

The  dolomites  found  at  Bowling  Green,  Ohio,  and  at  several 
points  in  the  State  of  New  York,  are  especially  good,  and  carry, 
in  some  cases,  after  burning,  over  40  per  cent,  of  magnesia.  The 
lime  should,  of  course,  be  well  burned,  should  slake  easily,  and  be 
as  free  as  possible  from  lime  and  silica.  The  following  analyses 
will  indicate  the  general  composition  of  lime  well  suited  for  use 
in  this  connection  :  — 


Silica,  etc  . 

0.05 

0.30 

trace 

Iron  and  alumina  sesquioxides    

0.65 

1.54 

0.18 

57.09 

55.99 

57.79 

40  88 

40.32 

40.24 

Carbonic  acid,  water,  etc.,  by  difference       . 

1  33 

1  85 

1.79 

If  lime  which  has  been  improperly  burned,  or  which  has  become 
air-slaked,  is  used,  the  proportion  of  base  is  likely  to  vary  to  such 
an  extent  as  to  cause  trouble,  and  such  limes  are  not  so  readily 
acted  upon  by  the  gas.  The  usual  proportion  for  making  up  the 


228  THE  CHEMI&TEY  OF  PAPER-MAKING. 

milk  of  lime  is  200  Ibs.  of  lime  per  thousand  gallons,  and  this 
should  give  a  liquor  of  9°  or  10°  T.,  carrying  about  3.50  per 
cent,  of  sulphurous  acid.  The  liquor  made  in  towers  runs  from 
7°  to  10°  T.,  and  usually  contains  a  slightly  greater  proportion 
of  free  sulphurous  acid,  or  acid  above  that  needed  to  form  bisul- 
phite, than  the  liquor  which  is  made  from  milk  of  lime.  It  is 
difficult  to  make  a  lime  liquor  in  practice  of  a  greater  density  than 
10°  T.,  but  where  magnesia  or  soda  is  used  without  lime  the 
magnesia  liquor  can  be  made  in  an  apparatus  like  Catlin's  to  stand 
25°  T.,  while  the  soda  liquor  can  be  brought  up  to  60°  T. 

The  following  analysis  may  be  taken  as  representative  of  a  well- 
made  liquor  prepared  from  dolomite :  — 

BISULPHITE  LIQUOR. 
Specific  gravity  at  15°  C.  =  1.0582. 


Per  cent. 

Sulphurous  acid  (S02) 4.41 

Sulphuric  acid  (SO3)  .     .     .     ....     .     .  0.13 

Lime  (CaO)  ...........  0.95 

Magnesia  (MgO)    . 0.72 

Silica  (SiO2) 0.04 

Combined  as :  — 

Sulphate  of  lime  (CaSO4) 0.22 

Bisulphite  of  lime  (CaS205) 2.84 

Bisulphite  of  magnesia  (MgS2O^)      .     .     .  3.04 

Free  sulphurous  acid  (S02) 0.11 

The  lime  and  magnesia  in  a  finished  liquor  never  bear  quite  the 
same  relation  to  each  other  as  in  the  dolomite  from  which  the 
liquor  was  prepared.  The  magnesia  is  always  somewhat  in  excess, 
as  a  portion  of  the  lime  is  unavoidably  thrown  out  as  sulphate  and 
monosulphite.  In  case  any  great  discrepancy  appears,  it  is  evidence 
that  too  much  air  has  been  admitted  to  the  sulphur  furnace,  or 
else  that  a  large  proportion  of  lime  is  being  lost  as  monosulphite 
in  the  sediment.  An  analysis  of  the  sediment  will  point  to  the 
proper  explanation. 

Although  the  loss  of  both  lime  and  sulphur  may  easily  be  con- 
siderable, it  is  so  insidious  that  it  will  probably  be  underestimated 
unless  careful  daily  records  are  kept  of  the  amounts  of  lime  and 
sulphur  used,  the  volume  of  liquor  made,  and  the  quantity  of  each 


THE  SULPHITE  PROCESS.  229 

chemical  which  analysis  shows  to  be  present  in  the  liquor.  Good 
liquor  may  be  made  even  where  large  losses  occur,  since  the  loss 
.comes  wholly  upon  the  lime  and  the  sulphur  combined  with  it, 
so  that  as  more  lime  is  lost  the  proportion  of  the  more  desirable 
bisulphite  of  magnesia  in  the  liquor  is  increased. 

The  loss  of  sulphur  is  due  to  dirt  and  ash,  to  subliming,  escape 
of  gas  through  imperfect  absorption,  and,  especially,  to  the  forma- 
tion of  sulphuric  acid  on  account  of  a  successive  supply  of  air. 
The  loss  from  dirt  should  not  amount  to  more  than  2  per  cent., 
and  5  per  cent,  should  cover  all  loss  from  moisture,  ash,  and  sub- 
limed sulphur.  Unless  great  care  is  exercised  the  loss  through 
formation  of  sulphuric  acid  may  easily  amount  to  20  or  30  per 
cent.  There  should  be  no  excuse  for  any  loss  of  sulphur  through 
imperfect  absorption  of  gas.  If  the  lime  used  has  not  been  freshly 
slaked,  or  if  it  has  become  air-slaked  in  storage,  a  considerable  loss 
will  always  be  found  between  the  lime  in  the  liquor  and  that 
weighed  off,  on  account  of  the  absorption  of  water  and  carbonic 
acid  from  the  air.  If  an  inferior  grade  of  lime  is  used,  it  is  likely 
to  contain  considerable  silica,  which  will  be  left  in  the  sediment. 
Improperly  burned  lime  carries  more  or  less  carbonic  acid,  and 
consequently  more  of  such  lime  must  be  used  to  obtain  the  same 
strength  of  liquor.  The  greater  part  of  the  loss  of  lime  is  due  to 
failure  to  bring  all  the  monosulphite  into  solution,  and  to  the 
formation  of  sulphate.  The  sediment  in  the  storage  tanks  should 
be  tested  before  it  is  thrown  away,  as  it  may 
pay  to  work  it  over  if  the  proportion  of 
monosulphite  is  very  large. 

It  sometimes  happens  that  the  sulphite  of 
lime  formed  in  the  middle  or  upper  tanks 
crystallizes  upon  the  paddles  of  the  appara- 
tus instead  of  going  into  solution.  This 
crystallization  usually  takes  a  peculiar  form, 
which  gives  the  paddles  the  appearance  of 
having  kernels  of  popped  corn  stuck  over 

them.      The  thickness    of   the    deposit  may  FlQ'  4*.  -  IWWUSTATIOIT 

OP  GaSO3. 
become  so  great,  unless   promptly   attended 

to,  as  to  cause  the  breaking  down  of  the  paddles,  and,  in  any 
case,  the  power  required  to  drive  the  apparatus  thus  inorusted 
becomes  much  greater  than  usual. 

Fig.  44,  which  is  taken  from  a  photograph  of  a  piece  of  paddlo 


230  THE  CHEMISTRY  OF  PAPER-MAKING. 

from  one  of  these  machines,  will  serve  to  give  an  idea  of  the  thick- 
ness sometimes  reached  by  this  incrustation.  Perhaps  the  easiest 
way  to  remove  the  deposit  is  to  let  down  one  or  two  charges  of 
water  instead  of  milk  lime.  As  the  gas  is  dissolved  by  the  water, 
the  sulphite  gradually  goes  into  solution. 

It  is  claimed  on  good  authority  that  the  addition  of  a  small 
amount  of  Solvay  ash  to  the  milk  of  lime  causes  much  better 
absorption  of  the  gas,  and  more  rapid  settling  of  the  liquor ;  while 
it  is  also  said  to  prevent  the  precipitation  of  sulphite  of  lime  in  the 
digester.  The  ash  is  added  in  proportion  of  2  to  5  per  cent,  on 
the  weight  of  the  lime,  and  with  it  is  used  about  the  same  weight 
of  common  salt.  If  the  desired  result  is  not  obtained,  the  amounts 
of  each  are  increased  in  successive  charges  of  liquor,  about  one- 
half  per  cent,  of  salt  being  added  for  each  additional  per  cent,  of 
ash.  Soda  crystals  without  the  salt  are  sometimes  used  in  the 
proportion  of  40  Ibs.  to  1000  gallons  of  milk  of  lime.  This  is 
equal  to  about  20  Ibs.  of  anhydrous  carbonate  of  soda. 

In  the  Crocker  process,  which  makes  use  of  a  solution  of  bisul- 
phite of  soda,  prepared  by  agitating  inonosulphite  of  lime  in  a 
solution  of  neutral  sulphate  of  sodium  and  then  charging  the  mix- 
ture with  sulphurous  acid,  crude  acid  sulphate  of  soda  is  roasted 
to  obtain  the  neutral  sulphate,  and  the  sulphite  of  lime  may  be 
made  by  adding  lime  to  the  waste  boiling  liquor.  This  last  method 
is  claimed  by  the  patentee  as  the  preferable  one;  but  when  the 
Waste  liquors  are  so  treated,  a  large  quantity  of  organic  matter 
comes  down  with  the  sulphite  and  makes  the  separation  difficult. 

Pumping.  —  Rotary  pumps,  so  placed  that  the  liquor  flows  into 
them  under  a  slight  head,  are  best  used  in  all  cases  for  pumping 
sulphite  liquors.  The  pump  should  never  be  placed  where  it  is 
necessary  to  prime  it,  or  use  a  foot-valve  on  the  suction-pipe.  It 
is  impossible  to  keep  such  a  foot-valve  tight,  owing*  to  the  crys- 
tallization of  inonosulphite  in  the  working  parts.  The  pump  should 
be  built  of  phosphor-bronze,  or  other  bronze  of  good  acid-resisting 
quality.  In  some  foreign  mills  an  acid  egg  similar  to  those  used 
for  vitriol  is  employed  for  pumping  liquor.  The  egg  is  a  lead-lined 
vessel,  provided  at  the  top  with  a  pipe  through  which  air  may  be 
forced  under  pressure.  The  liquor  is  run  into  the  egg  through 
one  pipe  until  it  is  nearly  full ;  the  valve  on  this  pipe  is  then 
closed,  and  air  forced  in  on  top  of  the  liquor,  by  which  means  the 
liquor  is  driven  out  through  the  delivery  pipe  leading  from  the 


THE  SULPHITE  PROCESS.  231 


bottom  of  the  egg.  Steam  injectors  have  been  used  in  some  mills 
in  this  country  for  transferring  liquor.  There  is  no  objection  to 
their  use,  if  the  liquor  is  discharged  directly  into  a  closed  digester, 
otherwise  considerable  sulphurous  acid  is  lost  through  the  heating 
of  the  liquor.  Where  nothing  is  to  be  gained  by  such  heating, 
the  use  of  the  injector  is  too  expensive. 

Storage  Tanks.  —  The  tanks  used  for  storing  liquor  may  be 
lined  with  6-lb.  sheet  lead  for  the  sides,  and  8-lb.  for  the  bottom. 
No  lining  whatever  is  necessary  when  the  tanks  are  of  the  ordinary 
circular  form.  In  such  cases,  however,  the  tanks  should  always 
be  first  made  tight,  with  water  or  steam,  before  any  liquor  is 
admitted.  If  this  is  not  done,  it  is  impossible  afterward  to  make 
them  tight,  on  account  of  the  crystallization  of  monosulphite  be- 
tween the  staves.  The  storage  tanks  should  be  covered  so  as  to 
prevent  escape  of  gas,  and  access  of  air,  though  it  is  not  necessary 
that  the  cover  should  be  perfectly  air-tight.  The  tanks  should  be 
so  placed  that  the  sediment  may  be  easily  washed  out  from  time 
to  time.  When  the  liquor  is  stored  in  quantity,  there  is  little 
loss  of  strength,  either  through  escape  of  gas  or  oxidation  to 
sulphate. 

In  order  to  obtain  clear  liquor  with  as  little  loss  of  time  as 
possible,  the  delivery  pipe  from  the  tank  should  be  attached  to 
some  form  of  float,  so  that,  in  pumping,  liquor  would  always  be 
drawn  from  the  top.  A  sufficient  length  of  stout  rubber  hose  may 
be  used  inside  the  tank,  and  should  be  attached  to  the  bottom  with 
a  lead  pipe  leading  to  the  pump.  The  other  end  of  the  hose  is 
attached  to  the  float,  which  may  be  a  box  of  sufficient  size,  made 
-of  copper,  and  hermetically  sealed.  Wood  soon  becomes  so  satu- 
rated with  the  liquor  as  to  be  useless  for  the  float.  The  best 
form  of  gauge  showing  the  height  of  liquor  in  the  tank  is  a  glass 
tube,  of  a  diameter  of  not  less  than  J-inch.  The  fitting  which 
secures  the  tube  to  the  tank  at  the  bottom  should  be  a  cross  with 
a  cock  on  both  the  horizontal  and  vertical  arms,  for, convenience 
in  keeping  the  tube  from  clogging  with  the  sediment. 

The  best  results  in  cooking  are  only  obtained  where  the  whole 
liquor  apparatus  is  so  run  as  to  secure  liquor  of  a  quality  as  nearly 
uniform  as  possible.  This  necessitates  close  attention  to  the  sul- 
phur-burning, air-supply  and  the  strength  and  quality  of  the  milk 
of  lime.  No  lime  from  a  new  quarry  should  ever  be  used  until  its 
composition  has  been  ascertained  by  analysis,  and  the  weight  to 


232 


THE  CHEMISTRY  OF  PAPER-MAKING. 


be  used  corrected  by  proper  allowance  for  any  impurity  it  may 
contain. 

Digesters  and  Digester  'Linings.  —  The  extremely  corrosive 
action  of  sulphurous  acid  and  bisulphites  upon  iron  renders  some 
form  of  lining  necessary  for  protecting  the  digester  shell.  All 
forms  of  iron  are  rapidly  attacked  by  the  acid,  especially  at  the 
high  temperatures  and  pressures  employed  in  this  process;  wrought 
iron  suffers  most  severely.  Corrosion  does  not  proceed  regularly 
over  the  surface,  but  instead  the  iron  is  deeply  pitted.  Steel 
resists  somewhat  better  than  wrought  iron,  and  cast  iron  suffers 
least  of  all. 

Fig.  45  is  from  a  photograph  of  a  piece  of  half-inch  wrought- 
iron  boiler  plate  cut  from  one  of  the  digesters  at  the  mill  of  the 
Richmond  Paper  Company,  and  shows  very 
well  the  extent  to  which  the  corrosion  may 
proceed.  The  digester  from  which  the  sample 
was  cut  had  been  in  use  two  and  a  half  years, 
under  conditions  which  it  is  only  fair  to  say 
were  much  harder  than  any  likely  to  be 
tolerated  now. 

The  curious  irregularity  with  which  the 
metal  was  corroded  is  especially  noticeable. 
The  iron  was  eaten  away  to  a  depth  of 
^-ineh  for  some  distance  along  a  line  just 
above  the  bottom  row  of  rivets  on  several 
of  the  plates.  In  other  places,  from  j-  to  -f$- 
inch  of  the  metal  was  gone.  The  average 
depth  to  which  the  shell  was  corroded  was 
at  least  -^-inch. 

Lead  is  the   only  common    metal  which 

resists  perfectly  the  action  of  the  liquor,  and  its  immunity  from 
corrosion  is  largely  due  to  the  almost  complete  insolubility  of 
its  sulphate,  which,  as  soon  as  formed,  makes  a  protective  coat- 
ing for  the  metal  underneath.  The  use  of  lead  in  this  connec- 
tion is  greatly  complicated  by  the  peculiar  behavior  of  the  metal 
when  subjected  to  frequent  variations  of  temperature  over  con- 
siderable range.  The  coefficient  of  expansion  of  lead  is  0.0000297, 
while  that  of  iron  is  only  0.0000123 ;  so  that  wherever  the  two 
metals  are  held  together  and  subjected  to  any  rise  of  temperature, 
there  is  a  constant  tendency  for  the  lead  to  pull  away  from  the 


FIG.  45.  —  CORRODED 
DIGESTER  SHELL. 


THE  SULPHITE  PROCESS.  233 

iron;  or,  in  the  case  of  a  lead  lining  contained  within  an  iron 
shell,  the  tendency  is  for  the  lining  to  grow  too  large  for  the 
shell.  This  tendency  is  exaggerated  still  more  by  the  peculiar 
fact  that  when  lead  has  been  expanded  by  heat,  it  does  not,  like 
most  metals,  resume  its  original  dimensions  upon  cooling,  but, 
apparently  owing  to  the  sluggish  movement  of  its  molecules,  it 
covers  somewhat  more  surface  than,  before,  being  made  at  the 
same  time  correspondingly  thinner.  This  causes  the  phenomenon 
known  as  "  crawling,"  the  lead  showing  a  tendency  to  pull  away 
in  one  direction  from  any  point  at  which  it  is  held.  If  held  by 
bolts,  the  bolt-hole  is  gradually  changed  in  form  from  a  circle  to  an 
ellipse,  while  if  the  lead  is  secured  through  the  flanges  of  the 
digester  sections,  it  gradually  crowds  out  through  them. 

Owing  to  this  continual  movement,  cracks  are  likely  to  appear 
wherever  the  lead  makes  a  turn  which  is  at  all  short.  The  crack 
usually  does  not  come  at  just  the  point  of  turning,  but  parallel 
with  it,  and  a  little  to  one  side. 

Contrary  to  the  usual  fact  in  regard  to  metals,  the  acid-resisting 
qualities  of  lead  are  considerably  enhanced  by  the  presence  in  the 
lead  of  certain  impurities  in  small  amount. 

Calvert  and  Johnson,  upon  whose  researches  the  following  table 
is  based,  took  lead  plates,  each  1  metre  square,  and  covered  them 
with  16  litres  of  sulphuric  acid  each.  After  ten  days  the  quantity 
of  lead  sulphate  formed  was  determined. 

Specific  gravity  of  Ordinary  lead,  Virgin  lead,  Pare  lead, 

acid  used.  grras.  Pb8©4.  grins.  PbSO4.  grme.  PbSO4. 

I.  1.842  67.70  134.20  201.70 

II.  1.705  8.35  16.50  19.70 

III.  1.600  5.55  10.34  16.20 

IV.  1.526  2.17  4.34  6.84 
V.  1.746  49.67  50.84  55.00 

VI.  1.746  51.91  54.75  57.41 

The  ordinary  lead  contained  :  lead,  98.82 ;  tin,  0.40 ;  iron,  0.36 ; 
copper,  0.40.  The  virgin  lead :  lead,  99.21 ;  tin,  0.01 ;  iron,  0.32 ; 
copper,  0.44.  In  the  first  four  experiments  pure  acid  was  used,  and 
at  the  ordinary  temperature ;  in  the  last  two,  commercial  acid  at  a 
temperature  of  about  50°  C. 

Other  experiments  indicate  that  small  quantities  of  antimony 
and  copper  make  lead  more  resisting  ;  while,  when  bismuth  is 
present,  the  lead  is  more  readily  attacked. 


234  THE  CHEMISTRY  OF  PAPER-MAKING. 


The  whole  object  of  the  many  ingenious  mechanical  devices 
which  have  been  embodied  in  the  lead  linings  of  sulphite  digesters 
is  to  hold  the  lead  in  place,  while  at  the  same  time  localizing  and 
diminishing  the  tendency  to  crawl.  The  thickness  and  weight  of 
the  lead  employed  varies  within  wide  limits  from  the  6-lb.  lead 
used  in  the  Mitscherlich  process  to  f-iuch  lead,  weighing  48  Ibs.  to 
the  square  foot,  as  at  one  time  used  in  several  mills  in  this  country. 
Generally  speaking,  the  thickness  of  the  lead  is  ^-inch,  correspond- 
ing to  a  weight  of  32  Ibs.  per  square  foot. 

The  present  rapid  introduction  of  cement  linings  has  so  changed 
the  conditions  of  the  sulphite  process  that  lead-lined  digesters  now 
have  hardly  more  than  a  historical  interest.  They  have  played 
so  important  a  part  in  the  development  of  the  process,  however, 
and  so  much  skill  in  chemical  engineering  has  been  expended  upon 
their  construction,  that  we  shall  consider  briefly  the  more  important 
of  the  different  types. 

One  of  the  earliest  devices  for  holding  the  lead  in  place  is  found 
in  the  rings  employed  by  Frank.  These  were  at  first  merely 
formed  of  lead  and  antimony  cast  in  half-circles,  and  burned 
together  inside  the  digester.  In  a  later  form,  advantage  was  taken 
of  the  greater  expansion  shown  by  brass,  and  the  rings  were  made 
of  brass  covered  with  lead ;  the  ring  thus  held  more  tightly  as  the 
temperature  in  the  digester  rose.  Still  later  the  ring,  instead  of 
being  continuous,  was  formed  in  three  segments,  held  in  place  by 
wedges,  which  could  be  tightened  up  as  the  lead  underneath  the 
ring  grew  thinner.  The  great  objection  to  all  forms  of  ring  is 
found  in  this  tendency  to  cut  and  squeeze  the  lead  beneath  so 
rapidly  that  frequent  repairs  are  necessary.  In  a  modified  form, 
however,  rings  have  been  used  in  several  of  the  most  satisfactory 
lead-lined  digesters  with  which  we  are  acquainted.  In  these  cases 
the  rings  were  made  of  wrought-iron  strips  2  inches  wide,  cut  in 
half -circles,  and  sprung  in  place  inside  the  digester.  They  were 
then  covered  with  ^-inch  lead,  which  was  burned  to  the  lining  on 
either  side.  The  rings  were  placed  18  inches  apart  through  the 
whole  length  of  the  digester. 

Partington  has  employed  several  different  .methods  for  holding 
the  lining  in  place  in  his  globe-shaped  rptaries,  and  they  are  all  of 
interest  in  connection  with  the  study  of  the  development  of  digester 
linings.  The  lead  itself  is  cut  in  sections,  having  the  form  of  a 
spherical  triangle  or  lune,  each  piece  being  of  sufficient  size  to 


THE  SULPHITE  PROCESS. 


235 


FIG.  46.  —  CLAMP. 


cover  -J^  of  the  interior.  In  the  earlier  linings  the  joints  at 
the  junction  of  the  various  pieces  were  burned,  so  that  the  lining 
formed  one  continuous  piece.  It  was  held  in  place  by  bolts  with 
large  washer-shaped  heads,  the  washer  being  on  the  interior  and 
the  nut  on  the  outside.  These  heads  were 
covered  with  lead  of  the  same  thickness  as 
that  used  for  the  linings,  and  the  covering 
was  burned  around  the  edge  to  the  lining. 
Rows  of  clamps  of  the  form  shown  in  Fig. 
46  extended  from  what  may  be  called  the 
poles  of  the  digester,  in  lines  similar  to  those 
marking  parallels  of  longitude  on  the  globe,  and  a  similar  row  of 
clamps  passed  round  the  digester  equatorially.  The  heads  of  the 
clamps  were  formed  of  iron  surrounded  by  cast  lead.  They  were 
held  in  place  by  bolts  passing  through  the  digester  wall,  and 
secured  with  a  nut  on  the  outside.  Makin  introduced  an  improve- 
ment (Fig.  47)  in  these  linings 
by  the  use  of  a  compound  lead 
and  iron  plate,  formed  of  a  sheet 
of  thin  boiler  iron  perforated  with 
numerous  half-inch  holes,  and 

covered  with  lead,  which  was  cast  upon  it  and  secured  by  the 
metal  which  flowed  through  the  holes.  An  objection  was  made  to 
this  cast  lead  on  account  of  the  numerous  pin-holes,  which  were 
difficult  to  avoid  in  casting  the  metal,  and  Makin's  lining  was  next 
prepared  by  taking  a  sheet  of  lead  of  the  usual  thickness  used  in 
lining,  laying  the  iron  plate  upon  it,  which  in  this  case  was  per- 
forated in  such  a  way  that  the  holes  were  considerably  smaller  at 
the  end  next  the  lead  than  upon,  the  upper  side,  and  pouring  melted 
lead  or  solder  into  these  holes  ;  Hojkd  sheet  lead  could  then  be 
used,  and  as  only  one  side  of 
the  iron  was  covered,  there 
was  considerable  saving  in  the 
former  metal.  A  somewhat 
similar  lining  was  adopted  by 
McDougall,  who  used,  in  place 

of  the  iron  plate,  stout  iron- wire  gauze  to  which  the  lead  was 
burned.  G.  W.  Russell  patented  in  this  country  a  compound 
lining,  formed  by  casting  lead  upon  a  heavy  wire  gauze  or  net- 
ting, as  shown  in  Fig.  48. 


FIG.  47.  —  MAKIN  LINING. 


FIG.  48.  — G.  W.  RUSSELL'S  LINING. 


236 


THE  CHEMISTRY  OF  PAPER-MAKING. 


Fig.  49  represents  a  digester  of  the  type  known  as  a  globe 
rotary,  lined  up  with  the  Makin  compound  plates.  As  this  lining 
was  at  first  applied,  the  joints  between  the  sections  b  were  covered 


FIG.  49. — PARTINGTON  ROTARY  DIGESTER. 

by  strips  of  sheet  lead,  shown  as  a  heavy  black  band  at  e.     These 
strips  were  soldered  or  burned  to  the  adjacent  edges  of  the  lining. 
A  later  form  of  the  Partington  lining  made  use  of  the  modifica- 
tion introduced  by  Springer.     In  this  method,  which  is  shown  in 

Fig.  50,  the  sections  of  the 
lining  are  so  placed  as  to 
leave  a  small  space  between 
adjacent  edges.  In  the  figure, 
A  represents  the  boiler  shell, 
and  a  the  compound  lead  and 
iron  plate,  invented  by  Makin. 
0  is  an  acid-resisting  packing 
of  asbestos,  or  asbestos  and  rubber,  between  the  edges  of  the 
plates.  Over  the  joint  is  laid  a  strip  of  sheet  packing, '£.  The 
sections  of  the  lining  are  held  in  place  by  means  of  stay  strips  B, 


FIG.  50.  —  THE  SPRINGER  LINING. 


THE  SULPHITE  PROCESS. 


237 


composed  of  a  perforated  metal  band,  «,  around  which  lead  has 
been  cast  after  the  method  followed  in  making  the  lining  itself. 
The  stay  strips  are  secured  by  bolts,  which  occur  at  frequent  inter- 
vals, and  whose  heads  are  covered  with  lead  as  shown. 


FIG.  61.  —  THE  RITTEK-KKLLNER  LINING. 

The  Ritter-Kellner  digesters  are  of  upright  form,  and  for  holding 
the  lead  in  position  the  main  reliance  is  placed  in  two  devices; 
the  first  of  these  consists  of  a  lead,  or  lead  and 
antimony  ring  sunk  in  the  digester  wall,  as 
shown  at  E  in  Fig.  51,  and  to  which  the  lead  is 
burned.  The  digester  wall  between  these  rings 
is  perforated  at  various  points,  and  rivets,  (7,  of 
hard  lead  are  driven  in  the  holes,  the  lining 
being  burned  to  them  on  the  inner  side.  The 
iron  shell  presents  a  perfectly  smooth  interior, 
all  joints  being  butt  joints,  and  all  rivets 
counter-sunk. 

The   earliest   form    of  the   Ekman   digester 
which  was  introduced  into  this  country  was  of 
small  size,  having  a  capacity  of  only  about  500  Ibs.  of  pulp,  and 
was  lined  with  16  Ibs.  lead.     At  the  upper  portion  of  the  digester 


FIG.  52. — EARLY 
EKMAN 


238 


THE  CHEMISTRY   OF  PAPER-MAKING. 


wall  a  recess  of  the  form  shown  in  Fig.  52  extended  around  the 
digester,  and  the  lead  lining  was  forced  into  this  recess  for  support. 
A  better  method  for  causing  the  lining  to  crack  could  hardly 
have  been  devised,  and  so  far  as  we  know  none  of  these  digesters 
are  now  in  use.  The  sectional  digesters  of  Wheelwright  which 
succeeded  them  also  gave  much  trouble  in  their  early  form, 
owing  to  the  cracking  of  the  lead  below  the  flanges,  and  the 
difficulty  of  making  joints  between  the  sections.  An  attempt  was 
made  to  overcome  this  by  making  the  lining  continuous,  and  burn- 
ing it  to  lead  rings  which  passed  between  the  flanges.  We  are 
of  the  opinion  that  this  is  a  fairly  good  form  of  lining,  but  at  the 
time  of  its  adoption  there  was  much  trouble  from  collapsing,  caused 
by  liquor  which  had  worked  its  way  between  the  lining  and  the 
shell,  only  to  be  again  converted  into  steam  when  the  digester 
was  blown  off. 

The  principle  of  the  Wheelwright  cast-iron  digester,  which  was 
designed  to  overcome  the  difficulties  arising  from  the  expansion 
and  crawling  of  the  lead  lining,  is  illustrated  in  Fig.  53,  which 
shows  a  section  through  one  ring.  The  rings  were  6Jor  7  feet  in 


FIG.  53. — WHEELWRIGHT  CAST-IRON  DIGESTER  (SECTION  THROUGH  ONE  RING). 

diameter  and  2  feet  high.  The  digester  was  built  up  of  ten  of 
these  rings,  with  top  and  bottom  cone  pieces.  It  will  be  noted  on 
inspection  of  the  figure  that  the  inner  wall  of  each  ring  curves  out- 
ward toward  the  flanges,  so  that  the  lining  always  lay  upon  convex 
curves,  while  any  expansion  was  at  once  taken  up  through  the 
flanges.  The  joints  at  the  flanges  were  made  tight  either  by  a 
packing  like  that  of  Jenkins  or  by  lead  rings  placed  just  inside  the 
bolt  holes,  at  which  point  a  slight  depression  will  be  noticed. 

The  Graham  boiler  is  built  up  of  compound  lead  and  iron  plates, 
and  has  the  lead  lining  secured  to  the  iron  at  every  point  of  con- 
tact. The  compound  plates  are  prepared  before  the  sheets  are  bent 
or  assembled.  The  iron  plate  is  cleaned  and  smoothed  very 


THE  SULPHITE  PEOCESti.  289 

fully  by  an  emery  wheel.  It  is  then  placed  over  gas  jets,  and  upon 
it  is  put  a  rectangular  frame  or  ledge,  the  joint  between  the  frame 
and  ledge  being  made  tight  by  a  fireproof  packing.  The  upper  sur- 
face of  the  plate  which  is  to  receive  the  lead  is  moistened  by  zinc 
chloride  solution,  and  when  the  temperature  of  the  plate  has  been 
raised  by  the  gas  jets  to  about  the  melting  point  of  lead,  the  molten 
lead  is  poured  on.  In  this  way  a  very  good  joint  between  the  two 
metals  is  secured,  and  it  is  claimed  that  it  is  impossible  to  cut 
away  the  lead  with  a  cold  chisel  without  leaving  a  thin  coating  of 
this  metal  upon  the  iron  plate.  An  uncoated  margin  for  the  joints 
and  rivets  is  left  on  each  plate,  and  after  the  plates  are  assembled, 
the  unprotected  lines  along  the  joints  are  similarly  coated  by  heat- 
ing locally  with  a  blow-pipe  and  running  in  melted  lead. 

The  difficulties  inseparably  connected  with  the  use  of  the  best 
lead  linings  led  to  the  introduction  of  digesters  built  of  bronze, 
capable  of  resisting  more  or  less  perfectly  the  action  of  the  sul- 
phite solution.  The  general  formula  for  these  bronzes  is  9  parts 
of  copper  to  1  part  of  tin;  but  each  manufacturer  has  his  own 
method  of  working  the  alloy,  and  thus  claims  to  secure  special 
properties. 

Martin  L.  Griffin  gives  the  composition  of  the  Schenck  digester 
metal  as  below :  — 

Per  cent. 

Tin     .     .    .     . 7.68 

Copper    ............     91.28 

Zinc    .............       0.89 

These  digesters  are  usually  built  of  the  cast  metal  in  3-foot 
sections,  having  in  some  cases  a  diameter  as  great  as  9  feet ;  the 
joints  between  sections  are  easily  made  tight  with  lead  rings,  as 
jthere  is  here  no  lining  to  be  cut.  It  is  undeniably  true  that  all 
such  digesters  are  acted  upon  to  a  considerable  extent  by  the  hot 
liquor,  as  may  be  readily  proved  by  taking  some  of  the  unwashed 
pulp,  drying  and  burning  it,  dissolving  the  ash  in  weak  acid,  and 
then  placing  for  a  moment  a  polished  knife-blade  in  the  solution, 
when  the  copper  will  be  deposited  upon  the  iron. 

Besides  the  corrosion  which,  in  spite  of  chemical  testimony,  was 
for  a  long  time  denied  by  the  builders  of  these  digesters,  they  are 
subject  to  other  and  perhaps  more  serious  elements  of  weakness. 
Recent  tests  show  that  the  strength  of  the  metal  is,  in  some  cases, 
reduced  fully  40  per  cent,  by  heating  to  the  temperatures  reached 


240 


THE  CHEMISTRY  OF  PAPER-MAKING. 


in  practice  in  these  digesters,  while  the  frequent  changes  of  tem- 
perature to  which  they  are  subjected  cause  in  time  a  crystallization 
of  the  metal,  which  greatly  impairs  its  power  to  resist  strain. 
The  significance  of  these  facts  has  been  emphasized  by  several 
disastrous  explosions. 

There  is  some  difference  of  opinion  as  to  the  relative  merit  of 
the  upright  and  rotary  form  of  digester.  Somewhat  less  liquor 
can  be  used  in  the  rotary,  and  there  is  no  danger  of  making  black 
chips,  as  none  of  the  chips  remain  uncovered  for  more  than  a 
minute  or  two  at  a  time.  The  upright  digesters  are  somewhat 
cheaper  to  build  and  keep  in  operation,  and  although  we  have  no 
satisfactory  explanation  to  offer  for  the  fact,  we  have  found  it  to 
be  generally  true,  that  pulp  made  in  an  upright  is  of  somewhat 
stronger  and  better  quality  than  that  produced  in  the  rotary. 

Many  forms  of  blow-off  valves  are  in  use  on  sulphite  boilers, 
and  a  poor  valve  causes  endless  trouble.  It  may  be  said,  in 
general,  that  gate  valves  are  not  well  suited  for  use  in  this  posi- 
tion, on  acoount  of  their  great  liability  to  become  clogged  from 


FIG.  54.  — CLAPP  VALVE. 


pulp  which  has  got  into  the  bonnet  of  the  valve  or  on  the  seat. 
Plug  cocks  are  better. 

The  Clapp  valve  (Fig.  54)  has  been  used  with  great  success  in 
the  soda  process,  and  possesses  many  points  of  merit  which  should 
make  it  readily  adaptable  to  sulphite  digesters.  Its  construction 


THE  SULPHITE  PROCESS. 


241 


FIG.  55.  —  BURNING- IRON. 


and  the  readiness  with  which  it  may  be  cleaned  are  apparent  from 

the  figure. 

The  steam-pipes  on  rotary  digesters  necessarily  pass  through  the 

trunnions,  and  usually  follow  the  curve  of  the  digester  for  a  short 

distance    on    the   inside. 

In  the  upright  digesters, 

steam  is  always  admitted 

at  the  bottom,  and  best 

through    a   8-inch    pipe. 

Various     devices      have 

been  used  foi    spreading 

the  steam  as  it  issues  from  the  pipe ;  but  they  are  objectionable, 

since  the  force  of  the  steam  is  thereby  much  diminished,  and  there 

is  considerably  more  likelihood  of  clogging  the  pipe  by  pulp  or 

incrustation.   With  the  steam-pipe  placed  at  the  apex  of  a  properly 

shaped  cone  bottom,  the  chips  themselves  spread  the  steam  suffi- 
ciently, and  there  is  no  danger  that  any  of  the 
chips  will  pack  to  one  side,  where  the  steam 
will  not  reach  them. 

All  lead-burning  inside  the  digester  is  done 
with  a  blow-pipe,  but  joints  can  be  more 
quickly  made  with  heavy  lead  by  the  use  of 
the  burning-iron,  whenever  the  seam  is  hori- 
zontal. 

Fig.  55  shows  the  shape  commonly  adopted 
for  such  irons,  which  usually  weigh  about  10 
Ibs.  Where  much  lead-burning  of  this  sort 
has  to  be  done,  it  is  advisable  to  employ  one 
•of  the  recently  invented  irons,  which  are  kept 
hot  by  an  electric  current,  since  by  their  use 
much  time  is  saved,  and  the  plumber's  helper 
can  usually  be  dispensed  with. 

A  good  form  of  plumber's  gas-machine  for 
use  in  lead-burning  is  shown  in  Fig.  56.  It 
consists  of  two  cylinders  made  of  heavy  sheet 
lead, -or  two  oil  barrels  may  .be  taken,  and 
lined  up  with  thin  sheet  lead.  The  vessels 
are  connected  by  a  rubber  tube  at  the  bottom, 

as  shown.     The  lower  cylinder  has  a  false  bottom,  and  the  space 

above  this   is  filled  with  granulated  zinc,  made  by   melting  the 


FIG.  56.  —  GAS 
MACHINE. 


242  THE  CHEMISTRY  OF  PAPER-MAKING. 

metal  and  pouring  it  in  water  from  the  height  of  a  few  feet. 
The  upper  cylinder  is  filled  with  dilute  sulphuric  acid,  which, 
upon  opening  the  cock,  flows  down  into  the  lower  cylinder, 
and  by  its  action  upon  the  zinc  causes  the  rapid  evolution 
of  hydrogen.  The  gas  is  led  away  to  the  blow-pipe  through 
a  rubber  tube  which  is  attached  to  the  small  pipe  leading  from 
the  top  of  the  bottom  tank.  The  pressure  of  the  gas  may  be 
regulated  roughly  by  the  height  at  which  the  upper  cylinder  is 
placed.  The  apparatus  is  self-regulating,  because,  as  soon  as  the 
cock  in  the  gas-pipe  is  closed,  the  pressure  of  the  gas  soon  forces 
the  acid  up  into  the  higher  cylinder,  and  away  from  the  zinc. 
The  evolution  of  gas  then  stops  until  a  new  supply  is  required. 

The  Mitscherlich  Digester  is  noticeable  from  its  large  size, 
and  the  fact  that  it  was  the  first  type  in  which  bricks  were  used 
as  a  portion  of  the  lining.  These  boilers  are  commonly  from 
12-14  feet  in  diameter,  and  from  36-40  feet  long.  Those  of 
the  smaller  size  hold  about  100  cubic  metres  of  wood  and  60  cubic 
metres  of  liquor.  They  have  two  manholes  at  the  top,  and  two  or 
three  at  the  bottom,  and  are  mounted  on  foundation  walls  at  least 
as  high  as  a  man.  There  is  so  much  expansion  in  these  boilers 
that  they  are  not  fastened  directly  to  the  walls,  but  instead  are 
supported  by  cast-iron  shoes  riveted  to  the  shell,  and  resting  upon 
iron  beams.  Sometimes  rollers  are  placed  between  the  shoes  and 
the  beam,  while  often  the  adjacent  surfaces  are  merely  planed  to 
give  a  well-faced  bearing. 

The  Mitscherlich  lining  consists,  first,  of  a  coat  of  tar  and  pitch, 
which  offers  some  protection  to  the  shell,  and  also  acts  as  a  cement 
to  hold  the  lining  of  thin  sheet  lead,  which  is  next  applied.  Upon 
the  lead  are  laid  two  courses  of  special  acid-resisting  bricks,  formed 
with  tongue  and  groove,  by  which  they  interlock.  Portland 
cement  is  sometimes  used  with  the  bricks,  which  in  any  case  are 
laid  flat  in  the  first  course,  and  edgewise  in  the  second.  In  some 
foreign  mills,  a  second  layer  of  lead  is  placed  between  the  bricks. 

The  boilers  are  heated  by  a  series  of  hard  lead  pipes,  which 
cover  the  lower  third  of  the  inside.  The  pipes  are  arranged  in 
four  sections  of  coils,  each  of  which  is  independent  of  the  others. 
The  steam  ends -of  alternate  coils  are  at  the  same  end  of  the  boiler, 
so  that  the  steam  in  the  adjacent  coils  is  passing  in  opposite 
directions.  The  total  length  of  pipe  in  a  single  digester  is  from 
1200-2600  feet.  The  digesters  are  fitted  with  safety-valve,  ther- 


THE  SULPHITE  PROCESS.  243 

mometer-tubes,  and  gauge-cooks  to  which  a  tube  is  temporarily 
attached  to  indicate  the  level  of  the  liquor  while  charging  the 
digester.  There  are  also  cocks  by  which  samples  of  liquor  may  be 
drawn  for  test  during  the  cook. 

Smaller  upright  digesters  in  two  sizes  are  offered  by  the  owners 
of  the  Mitseherlich  patents,  the  sizes  being  16  x  10  and  24  x  14. 

The  expense  and  difficulty  which  attend  the  operation  of  even 
the  best  types  of  lead-lined  boilers  have  caused  the  chemists  and 
others  engaged  in  the  development  of  the  process  to  look  long 
and  carefully  for  some  other  means  of  protection  which  should 
prove  more  manageable  and  less  costly.  One  of  the  earliest  at- 
tempts in  this  direction  is  described  in  United  States  patent 
851,330,  granted  to  one  of  the  authors.  In  this  case,  the  interior 
of  a  cast-iron  digester  6  inches  in  diameter  by  20  inches  high  was 
coated  with  an  enamel  composed  of  one  part  of  borate  of  lead  to. 
ten  parts  of  litharge.  This  enamel  has  a  low  fusing-point,  is  veiy 
tenacious,  and  resists  the  action  of  the  liquor  at  least  as  well  as 
lead.  The  difficulty  of  perfectly  coating  so  large  a  casting  proved 
so  great,  however,  that  only  one  digester  thus  protected  was 
put  in  operation,  and  this  developed  numerous  spots  where  scale 
beneath  the  enamel  prevented  its  adhering  to  the  metal.  At 
about  the  same-  time,  a  white  enamel  was  brought  forward  by 
Frambach. 

The  present  greatly  improved  methods  of  lining  up  digesters 
are  the  result,  in  the  main,  of  the  work  of  Pierredon,  Briingger, 
Mitscherlich,  Weiizel,  and  Kellner,  in  Europe,  and  of  G.  F.  Russell 
and  Curtis  and  Jones,  in  this  country, 

The  Salomoii-Bruiiggrer  Boiler.  —  About  1883  Briingger,  who 
was  chemist  in  Salomon's  mill  at  Cunnersdorf,  was  led  in  the 
course  of  some  temporary  repairs  to  substitute  within  a  digester 
a  short  length  of  iron  pipe  for  the  bronze  one  by  winch  steam  was 
ordinarily  supplied.  Upon  examining  this  pipe  at  the  end  of  the 
cook,  he  found  it  firmly  coated  with  a  thin  but  dense  scale  of 
sulphite  of  lime,  which  had  apparently  protected  the  metal  from 
corrosion.  Acting  upon  this  hint,  he  soon  had  a  digester  in  opera- 
tion, in  which,  by  appropriate  means,  this  scale  was  formed  over 
the  entire  interior  as  a  substitute  for  the  lead  lining  previously  in 
use.  It  is  necessary,  in  order  to  secure  the  coating,  that  the  heat 
be  transmitted  through  the  metal  to  the  liquor  within ;  and  for 
this  reason  digesters  of  this  type  are  heated  by  a  steam  jacket. 


244  THE  CHEMISTRY  OF  PAPER-MAKING. 

In  its  present  form  the  Salomon-Briingger  boiler  consists  of  two 
distinct  parts ;  an  inner  shell  of  welded  steel  which  is  from  6  feet 
6  inches  to  7  feet  in  diameter,  and  an  outer  shell,  also  of  steel,  but 
riveted.  The  cone  and  throat  of  the  inner  shell  are  of  cast  bronze, 
and  to  this  cone  is  riveted  the  outer  shell  or  jacket.  In  order  to 
allow  for  differences  in  expansion,  the  joint  between  the  two  shells 
at  the  bottom  is  made  by  a  stuffing-box.  The  total  length  over  all 
is  about  30  feet.  In  all  its  mechanical  features  this  digester  merits 
the  highest  praise. 

In  order  to  secure  the  protective  coating,  the  pressure -in  the 
jacket  is  brought  to  about  40  Ibs.  before  the  liquor  is  admitted. 
The  latter  upon  coming  in  contact  with  the  hot  metal  is  decom- 
posed in  part,  and  there  is  deposited  over  the  metal  a  thin  but 
excessively  hard  and  impervious  crust  of  sulphite  of  lime,  with 
perhaps  some  sulphate.  It  is  claimed,  and,  as  we  believe,  properly, 
that  a  crust  ^-inch  thick  (2-3  mm.  Reuleaux)  affords  complete 
protection.  There  is  at  most  a  merely  superficial  blackening  of  the 
shell.  No  especial  reliance  is  placed  upon  the  acid-resisting  quality 
of  the  bronze  cone,  but  this,  like  the  steel  shell,  is  protected  by  the 
lining.  In  order  to  secure  protection  at  this  point,  the  digester 
is  completely  filled  with  liquor  up  to  within  a  few  inches  of  the 
manhole  cover.  With  the  expansion  of  the  liquor  it  becomes  nec- 
essary to  blow  off  a  little  from  time  to  time,  when,  in  case  the 
liquor  falls  below  the  level  indicated,  sufficient  water  is  pumped 
in  to  supply  the  deficiency.  The  liquor  itself  is  used  clear,  and 
is  the  ordinary  bisulphite  solution. 

With  each  successive  cook  the  scale  increases  somewhat  in 
thickness,  while  any  places  which  have  been  laid  bare  where  the 
lining  has  flaked  off  are  freshly  coated.  Too  thick  a  lining  is 
undesirable,  not  only  because  the  tendency  to  flake  off  is  much 
increased  with  any  irregularity  in  thickness,  but  also  because  the 
thicker  scale  unnecessarily  retards  the  transmission  of  heat,  into 
the  boiler.  For  this  reason  it  is  customary  about  once  a  month, 
or  when  the  scale  has  reached  a  thickness  of  about  ^-inch,  to 
remove  the  scale  by  hammering.  The  same  result  may  be  attained 
by  the  use  of  a  more  acid  solution,  but  this  necessitates  the  prep- 
aration of  a  special  liquor,  and  is  otherwise  objectionable,  as  there 
is  some  danger  that  the  metal  may  be  corroded. 

The  records  of  the  mill  at  Cunnersdorf  show  that  whereas  in 
a  certain  digester  210  boilings  were  made  in  a  given  length  of 


THE  SULPHITE  PROCESS.  245 

time  when  working  with  a  lead  lining,  300  boilings  were  made 
in  this  digester  in  the  same  length  of  time  after  adoption  of  the 
protective  crust. 

The  Jung  and  Lindig  method  of  lining  depends  upon  the  forma- 
tion, upon  the  digester  wall,  of  a  coating  of  the  double  silicate  of 
iron  and  lime,  protected  further  by  one  of  silicate  of  lime.  Before 
applying  the  lining  the  inner  surface  of  the  digester  is  first  thor- 
oughly cleaned  with  wire  brushes  and  a  strong  alkaline  solution. 
This  is  followed  by  a  wash  of  dilute  sulphuric  or  hydrochloric  acid 
to  remove  the  alkali,  and  the  excess  of  acid  is  rubbed  off  with 
waste. 

The  clean  surface  of  the  metal  is  then  painted  with  ordinary 
sulphite  liquor  made  from  lime,  with  the  result  that  a  thin  coat 
of  the  double  sulphite  of  lime  and  iron  is  formed.  After  this  is 
dry  it  is  brushed  over  with  a  solution  of  water  glass,  in  order  to 
obtain  the  double  silicate  of  calcium  and  iron :  and  this  coat  is  also 
allowed  to  dry,  and  then  repeated.  The  coating  of  double  silicate 
so  obtained  is  finally  covered  with  a  pasty  mass  from  1  to  5  centi- 
metres thick,  of  a  mixture  of  dry  calcium  monosulphite  and  water 
glass.  The  proportions  used  are  5  to  30  parts  by  weight  of  the 
monosulphite  and  50  parts  by  weight  of  water  glass.  If  desired, 
100  parts  of  ground  Chamotte,  quartz  sand,  powdered  glass,  or 
asbestos  powder  may  be  added,  according  to  circumstances.  The 
proportions  of  the  various  ingredients  may  be  changed  as  desired 
to  produce  the  object  in  view,  which  is  a  solid,  adhering,  earthen- 
ware-like coating,  which  should  become  quite  hard. 

The  digester  is  now  ready  for  the  first  boiling  with  sulphite 
solution,  causing  the  formation  of  soluble  sodium  sulphite  which 
goes  into  solution,  and  of  silicate  of  lime  in  the  hardened  mass. 
The  latter  compound  is  very  acid-resisting,  and  is  capable  of  pro- 
tecting any  metallic  surface  from  the  erosive  action  of  sulphurous 
acid.  It  is  advisable  to  repeat  the  coating  of  monosulphite  and 
water  glass,  with  or  without  the  addition  of  such  bodies  as  quartz 
sand,  etc.,  after  a  few  boilings,  so  as  to  obtain  several  layers  of 
silicate..  Valves  and  tubing  after  being  cleaned,  a&  above  described, 
are  filled  with  a  solution  of  bisulphite  of  lime  and  well  warmed ; 
then  emptied,  filled  up  with  water-glass  solution,  emptied,  and 
dried.  They  are  then  boiled  in  a  solution  of  bisulphite  of  lime, 
and  treated  again  with  water  glass,  repeating  this  process  until 
a  sufficiently  thick  coating  of  silicate  is  obtained. 


246  THE  CHEMISTRY  OF  PAPER-MAKING. 

The  mixture  of  water  glass  and  monosulphite  of  lime  soon  grows 
hard,  and  constantly  becomes  denser  and  harder,  in  contact  with 
sulphite  solution ;  further,  the  coating  sticks  very  closely  to  the 
iron  or  steel,  owing  to  the  presence  of  what  corresponds  to  a  rust 
cement ;  and  finally,  the  difference  between  the  coefficient  of 
expansion  affects  only  the  fifth  decimal  place,  and  hence  can  be 
assumed  to  be  identical  with  that  of  iron. 

Cement  JLin ings.  —  Various  linings  composed  of  so-called  acid- 
proof  cements  are  at  the  present  writing  being  rapidly  introduced 
in  this  country  and  abroad.  One  of  the  earliest  as  well  as  one  of 
the  most  successful  of  these  cement  linings  is  that  of  Wenzel. 
By  his  method  cement  blocks  are  formed  in  wooden  molds  made 
to  conform  to  the  curvature  of  the  different  portions  of  the 
digester,  and  are  then  assembled  and  cemented  in  place  within 
the  boiler.  The  special  cement  used  is  for  the  most  part  a  mix- 
ture of  Portland  cement  and  silicate  of  soda.  The  thickness  of 
the  blocks  varies  with  the  size  of  the  boiler  and  the  position  for 
which  the  block  is  intended ;  those  for  the  bottom  of  the  digester 
being  made  thicker,  to  withstand  the  greater  wear.  The  usual 
limits  of  thickness  are  from  60-200  mm.  Rotaries  having  a  diam- 
eter of  2.5-3  metres  require  a  lining  80-100  mm.  thick,  while 
70-80  mm.  is  sufficient  for  those  of  2-2.5  metres  diameter.  The 
blocks  for  a  4-metre  Mitscherlich  boiler  are  made  125  mm.  in 
thickness. 

After  lining  by.  this  system,  the  boiler  is  heated  by  steam  for 
several  hours,  to  a  temperature  of  140°-160°  C.  By  this  treat- 
ment, cracks  are  opened  in  thin  or  weak  places,  and  are  cut  out 
and  refilled.  The  heating  is  then  repeated  until  no  more  cracks 
appear.  The  lining  is  finally  completed  by  covering  the  blocks 
with  a  coating  of  the  very  fine  cement,  which  is  put  on  to  a  depth 
of  4-5  mm.  This  wears  away  in  two  to  three  months,  but  may  be 
replaced  in  a  few  hours. 

Wenzel,  in  some  cases,  first  lines  the  digester  with  iron  wire 
lath,  upon  which  the  cement  lining  is  then  formed. 

Kellner  has  several  recent  patents  for  cement  linings,  among 
them  being  the  British  patents  numbered  6951,  15,980,  15,931,  all 
issued  in  1890.  Kellner's  cements  are  made  of  ground  slate  and 
silicate  of  soda,  or  of  powdered  slate  and  glass  and  Portland 
cement,  and  they  are  either  put  on  in  the  plastic  condition,  or  in 
the  form  of  blocks  or  slabs.  In  one  case  the  digester  is  first  lined 


THE  SULPHITE  PROCESS.  247 

with  the  mixture  of  ground  slate  and  silicate  of  soda,  and  after 
this  has  set,  a  second  layer,  composed  of  one  part  ground  slate,  two 
parts  ground  glass,  and  one  part  Portland  cement,  is  applied. 
Kellner  has  also  patented  in  this  connection  the  use  of  a  lining 
composed  of  slabs  of  tempered  glass  laid  upon  such  a  cement 
backing. 

G.  F.  Russell,  at  Lawrence,  began  experiments  with  cement  lin- 
ings, applied  directly  to  the  shell  in  the  plastic  state,  about  1888. 
In  the  earlier  linings,  a  mixture  of  Portland  cement  and  sand  was 
used,  but  the  sand  was  found  to  detract,  if  anything,  from  the 
durability  of  the  lining,  and  his  present  excellent  results  are 
obtained  by  the  use  of  Portland  cement  alone.  This  is  in  most 
cases  reinforced  by  a  facing  of  special  brick  or  tile,  as  shown  in 
Fig.  57.  The  usual  thickness  of  the  cement  lining  is  about  four 


i"iG.  57. — RUSSELL  LINING. 

inches.  Where  an  old  digester  is  relined  by  this  method,  this,  of 
course,  involves  a  serious  curtailment  of  production  ;  but  since  the 
introduction  of  these  linings  the  general  tendency  has  been  to 
build  the  new  digesters  of  very  much  larger  size.  The  shape  of 
the  upright  digesters  has  also  been  materially  changed  to  good 
advantage.  In  place  of  the  well-known  cone  at  top  and  bottom, 
the  top  is  now  formed  by  gradually  drawing  in  the  shell  in  a  gentle 
curve,  starting  nearly  from  the  centre,  as  shown  in  Fig.  58,  which 
is  taken  from  one  of  the  digesters  recently  built  for  the  Waldhof 
Zellstoff-Fabrik.  The  dimensions  given  are  in  millimetres.  Some 


248 


THE  CHEMISTRY  OF  PAPER-MAKING. 


digesters  of  this  type  building  in  this  country  have  the  bottom 
formed  after  the  same  manner  as  the  top  here  shown.      These 


FIG.  58.  —  CEMENT-LINED  UPRIGHT  DIGESTER. 

forms  of  construction  possess  the  advantage  of  much  diminishing 
the  tendency  which  the  older  forms  had  to  spring  slightly  under 
pressure,  and  so  open  cracks  in  the  cement  where  the  cones  joined 


THE  SULPHITE  PROCESS.  249 

the  body  of  the  boiler.  The  throat  at  either  end  may  be  protected 
by  a  bronze  or  lead  sleeve  passing  down  flush  with  the  lining. 
Either  metal  beneath  the  lining  or  bronze  or  lead  and  antimony 
pipes  passing  through  it  is  likely  to  cause  cracks,  due  to  the 
greater  expansion  of  the  metal. 

All  cement  linings  are  more  or  less  porous  when  first  applied, 
but  in  use  soon  fill  up  with  sulphate  and  sulphite  of  lime.  They 
then  become  practically  impervious  to  the  liquor,  and  afford  com- 
plete protection  to  the  shell  beneath.  Such  liquor  as  may  work 
through  a  crack  is  quickly  rendered  harmless  through  reaction 
with  the  lime  salts  composing  the  cement.  If  the  lining  is  built 
up  in  layers,  the  joint  between  the  fresh  and  partially  set  cement  is 
likely  to  be  defective,  and  the  crystallization  of  lime  salts  within 
the  lining  at  this  point  will  often  cause  the  outer  layer  to  loosen 
and  flake  off.  This  is  avoided  by  grouting  the  plastic  material 
in  between  the  digester  wall  and  a  movable  backer. 

Neither  Portland  cement  nor  any  of  the  more  complex  mixtures 
which  have  in  some  cases  been  adopted  resist  entirely  the  action  of 
the  liquor.  There  is,  moreover,  a  gradual  erosion  of  the  lining, 
caused  by  the  friction  of  the  chips  and  pulp.  From  these  causes, 
and  from  occasional  flaking  off,  there  is  always  more  or  less  of  the 
cement  in  the  pulp  as  discharged  from  the  digester,  but  the 
particles  are,  in  nearly  every  case,  so  heavy  that  passage  through  a 
short  sand-settler  is  sufficient  to  hold  them  back.  Such  trouble 
as  may  be  due  to  this  cause  is  in  large  measure  obviated  by  facing 
the  lining  with  well  baked  brick  or  tile. 

In  the  selection  of  these  bricks,  attention  should  be  had  to  the 
following  points :  They  should  be  very  hard  and  dense,  and  should 
not  absorb  more  than  2  per  cent,  of  their  weight  of  water,  after 
being  immersed  for  twenty-four  hours  in  that  liquid.  They  should 
contain  no  considerable  amount  of  iron  or  manganese,  and  should 
be  hard  baked  and  very  well  annealed.  Several  brands  of  paving 
and  other  special  brick  which  meet  all  these  requirements  are  now 
made  in  this  country.  Bricks  which  are  soft  or  under  burned  are 
very  apt  to  split  and  crack  under  the  changes  of  temperature  to 
which  they  are  subjected,  and  then  to  come  away  in  the  pulp. 
These  troubles  at  their  worst  are  slight  in  comparison  with  those 
which  attend  the  working  of  lead  linings,  while  the  cheapness  of 
cement  linings  and  the  readiness  with  which  such  slight  repairs  as 
they  require  may  be  effected  are  sufficient  to  ensure  their  general 
introduction. 


250  THE  CHEMISTRY  OF 


The  pulp-digester  invented  by  Messrs.  Curtis  and  Jones,  and 
first  put  in  operation  at  the  mill  of  the  Rowland  Falls  Pulp  Com- 
pany, embodies  several  novel  and  valuable  features,  and  has  a 
remarkable  record  for  durability  and  successful  work  in  practice. 
The  essential  novelty  of  this  apparatus  is  found  in  the  lining, 
which  is  composed  of  blocks  of  artificial  stone  so  shaped  that  they 
lock  into  each  other  when  in  place.  This  stone  is  preferably 
composed  of  Portland  cement  and  ground  glass  or  quartz,  to  which 
sometimes  is  added  a  percentage  of  soluble  glass.  The  density 
and  acid-resisting  qualities  of  these  materials  are  greatly  aug- 
mented by  the  process  to  which  they  are  subjected  in  the  manu- 
facture of  the  stone. 

The  objection  to  the  continuous  cement  lining,  applied  in  a 
plastic  state,  is  that  it  is  impossible  to  make  the  lining  of  uniform 
density.  Hence,  it  is  often  defectively  porous  in  spots,  and  thus 
liable  to  be  permeated  by  the  acid.  This  is  avoided  in  the  present 
instance  by  subjecting  the  blocks  to  pressure  during  the  molding 
operation,  which  makes  them  uniformly  dense  and  strong.  The 
blocks  are  then  exposed  for  a  time  to  an  atmosphere  of  carbonic 
acid  gas,  by  which  their  power  of  resisting  the  acid  and  the  me- 
chanical attrition  of  the  pulp  is  very  greatly  increased.  Digesters 
thus  lined  have  been  in  operation  for  a  year  without  showing 
appreciable  signs  of  wear,  and  without  entailing  any  expense  for 
repairs.  They  are  at  the  present  time  being  rapidly  introduced. 

Boiling.  —  In  spite  of  the  many  different  systems  under  which 
the  sulphite  process  is  worked,  the  process  of  boiling  is  carried  on 
by  all  of  them,  with  one  exception,  in  practically  the  same  way,  so 
far  as  strength  of  liquors,  temperatures,  and  time  are  concerned. 
The  exception  noted  is  found  in  the  Mitscherlich  process,  which 
will  for  that  reason  be  considered  by  itself,  after  taking  up  the 
processes  in  which  boiling  is  conducted  at  comparatively  high 
pressures  and  concluded  in  a  comparatively  short  time. 

It  is  customary,  in  charging  the  digester,  to  fill  it  as  completely 
as  possible  with  the  chips,  since,  before  the  full  pressure  is  reached, 
the  chips  will  settle  sufficiently  to  be  entirely  covered  with  the 
liquor.  The  liquor  should  be  run  in  as  rapidly  as  possible  ;  and  a 
6-inch  pipe  is  none  too  large  for  this  purpose,  as  much  time  may 
be  needlessly  wasted  through  the  use  of  a  small  pipe.  About 
2500  gallons  of  liquor  is  the  proper  amount  for  a  digester  carrying 
2  cords  of  chips.  The  strength  of  the  liquor  may  vary  consider- 


THE  SULPHITE  PROCESS. 


251 


ably,  if  the  tempera ture  is  regulated  to  correspond,  but,  in  gen- 
eral, liquor  of  10°  T.,  carrying  about  3£  per  cent,  sulphurous  acid, 
gives  the  most  satisfactory  results.  It  is  very  important  that  the 
pressure  should  not  be  run  up  too  fast,  and  at  least  four  hours 
should  be  taken  in  reaching  full  pressure.  If  the  heating  is  forced 
at  the  commencement  of  the  cook,  the  steam,  striking  the  cold 
liquor,  causes  a  violent  hammering  which  may  seriously  strain  the 
digester ;  but  a  more  serious  objection  is  found  in  the  effect  upon 
the  pulp.  When  the  pressure  is  hurried,  a  high  temperature  is 
reached  before  the  liquor  has  had  time  to  penetrate  to  the  interior 
of  the  chips.  The  wood  inside  is  more  or  less  burned  in  conse- 
quence, and  the  pulp  is  filled  with  chips  showing  a  hard,  red  or 
brown  central  portion.  Wherever  such  red  chips  are  found  in  the 
pulp,  the  cause  may  be  attributed  to  getting  up  pressure  too  fast. 
The  liquor  prevents  the  oxidation  of  the  wood,  and  it  is  necessary 
that  the  wood  should  be  thoroughly  permeated  before  there  is  any 
considerable  rise  of  temperature.  The  maximum  pressure  carried 
may  range  from  65  to  85  Ibs.,  the  higher  pressure  being  only  safe 
when  the  liquor  is  strong  in  sulphurous  acid.  The  pressure,  how- 
ever, affords  a  very  unreliable  indication  of  the  conditions  under 
which  the  operation  is  being  carried  on,  and  in  all  cases  the  main 
reliance  should  be  placed  upon  the  temperatures  as  shown  by  the 
thermometer.  The  temperature  is  the  real  factor  in  the  disinte- 
gration of  the  wood,  and  the 
pressure  carried,  except  so  far 
as  it  indicates  temperature, 
is  of  comparatively  slight 
importance.  It  may  be  due 
in  a  large  part  to  gas  set 
free  during  the  boiling,  and 
in  some  cases,  where  much 
condensed  water  is  formed, 
the  pressure  may  be  almost 
wholly  hydrostatic.  In  most 
mills,  the  thermometer  is 
placed  on  top  of  the  digester, 
or  in  the  blow-off  pipe ;  and, 
while  in  these  places  it  may  give  comparative  readings  which  are 
of  value,  the  true  temperature  of  the  digester  is  probably  somewhat 
higher  than  that  shown.  The  proper  place  for  the  thermometer  is 


FIG.  59.  —  SIDE  OIL  BATH. 


252  THE  CHEMISTRY  OF  PAPER-MAKING. 

about  one-third  of  the  way  down  on  the  digester  wall.  An  oil 
bath  may  be  easily  arranged  there  for  its  reception  by  passing  a 
drop  tube  of  bronze  through  the  digester  wall  and  lining,  as  shown 
in  Fig.  59.  A  still  better  arrangement,  however,  is  made  possible 
by  the  recent  introduction  of  what  is  known  as  the  Standard  ther- 
mometer. That  portion  of  the  instrument  carrying  the  metallic 
spring  passes  through  the  digester  wall,  while  the  dial  and  pointer 
on  the  outside  show  the  temperature  as  upon  a  steam  gauge.  By 
a  slight  modification  this  thermometer  can  be  made  to  indicate 
the  gas  pressure  in  the  digester  as  well  as  the  temperature.  It 
is  only  necessary  to  have  printed  on  the  dial  the  steam  pressures 
corresponding  to  the  various  temperatures.  The  difference  between 
the  pressure  shown  on  the  thermometer  and  that  shown  by  the 
steam  gauge  is  due  to  gas.  An  electrical  attachment  may  be 
applied  to  those  thermometers,  by  means  of  which  the  temperature 
carried  may  be  indicated  at  the  office,  or  in  any  part  of  the  mill. 
In  the  quick  cooking  processes,  the  best  results  in  boiling  are 
secured  when  the  highest  temperature  carried  is  from  300°  to 
312°  F. 

As  the  boiling  progresses,  the  effect  of  heat  and  the  reactions 
going  on  inside  the  digester  is  to  cause  more  or  less  gas  to  leave 
the  liquor,  and  the  amount  of  gas  pressure  increases  with  some 
regularity  to  the  end  of  the  coo'k.  With  a  properly  built  digester 
this  gas  pressure  is  no  detriment,  provided  the  temperature  is 
watched  and  carried  to  the  proper  point.  It  is  the  custom  in  most 
mills,  however,  to  blow  this  gas  off  at  intervals,  which  are  more 
frequent  in  the  last  stages  of  the  process.  There  is  an  impression 
in  some  quarters  that  if  this  is  not  done  the  gas  will  burn  the  pulp ; 
but  this  is  quite  erroneous,  since  it  is  the  high  temperature  and 
the  absence  of  sufficient  gas  which  causes  burning.  If  so  much 
gas  pressure  is  observed  that  blowing  off  becomes  necessary,  it 
merely  proves  that  the  liquor  was  too  strong  at  the  start,  and  that 
the  manufacturer  has  gone  to  the  expense  of  putting  an  unneces- 
sary amount  of  gas  into  the  liquor,  only,  in  most  cases,  to  waste 
it  in  the  boiling  operation. 

There  is  also  great  danger,  if  too  much  gas  is  blown  off,  that  the 
pulp  wall  be  burned;  in  fact,  wherever  burned  pulp  is  obtained 
when  the  temperature  has  not  been  allowed  to  rise  above  320°  F., 
it  may  be  inferred  that  the  liquor  was  originally  too  weak  or  that 
too  much  gas  was  blown  off. 


THE  SULPHITE  PROCESS.  253 

Unless,  however,  dry  and  hot  steam  is  used,  so  much  condensed 
water  may  form  in  the  boiler,  that  blowing  off  is  necessary  in  order 
to  keep  down  the  volume  of  liquor  and  prevent  a  hydrostatic 
pressure. 

We  have  already  pointed  out  the  great  insolubility  of  the  mono- 
sulphite  of  lime,  as  well  as  the  fact  that  it  is  easily  held  in  solution 
when  the  extra  equivalent  of  gas  necessary  to  form  the  bisulphite 
is  present.  Bisulphite  of  lime  is  a  very  unstable  salt  from  which 
the  extra  equivalent  of  sulphurous  acid  may  be  easily  driven  off 
by  heat,  with  formation  of  the  monosulphite.  As  sulphite  liquors 
rarely  contain  more  than  a  very  small  percentage  of  sulphurous 
acid  above  the  amount  needed  to  form  the  bisulphite,  it  is  evident 
that  when,  during  boiling,  any  of  this  gas  is  blown  off,  an  equiva- 
lent amount  of  monosulphite  of  lime  is  deposited  in  the  digester, 
where  it  either  causes  trouble  through  rendering  the  pulp  very 
difficult  to  wash,  or,  quite  commonly,  by  the  formation  of  a  hard 
incrustation  around  or  in  the  steam  and  blow-off  pipes.  We  have 
seen  the  inside  diameter  of  a  3-inch  steampipe  reduced  by  such 
incrustation  to  less  than  |-inch,  while  elsewhere  in  the  lower  por- 
tion of  the  digester,  the  scale  was  |-inch  thick. 

In  order  to  lessen  these  difficulties,  Kellner  heats  the  bisulphite 
solution  in  a  separate  vessel,  from  which  it  is  run  hot  into  the 
digester.  Much  of  the  monosulphite  is  thus  precipitated  outside 
the  boiler,  arid  may  be  redissolved  for  further  use  by  the  sulphu- 
rous acid  blown  off  during  treatment  of  the  wood.  British  patent 
No.  12,970,  A.D.  1891. 

Strainers  have  been  used  in  various  digesters  and  for  different 
purposes.  In  some  cases  a  strainer  bottom  of  iron  covered  with 
lead  is  placed  on  a  slant  within  a  foot  or  two  of  the  bottom  of  the 
digester.  In  this  case  the  digester  discharges  through  a  pipe  at 
the  side  near  the  bottom,  and  steam  is  admitted  under  the  false 
bottom.  The  strainer  here  serves  to  spread  the  steam,  and  is  by 
some  thought  to  secure  a  better  circulation  of  the  liquor,  but  its 
value  in  this  position  is  very  doubtful.  In  some  digesters  abroad 
a  strainer  was  formerly  placed  inside  the  digester,  and  about  one- 
quarter  the  way  down,  and  the  digester  was  only  filled  with  chips 
up  to  the  strainer,  which  carried  a  central  piece  which  was 
removed  during  filling.  The  object  of  the  strainer  in  this  position 
was  to  prevent  the  chips  from  rising  to  the  surface  of  the  liquor, 
where  they  might  carbonize  and  form  black  chips  which  seriously 


\ 


254  THE  CHEMIST&Y  OF  PAPER-MAKING. 

impaired  the  value  of  the  pulp.  The  output  of  the  digester  was, 
however,  greatly  curtailed*  and  the  black  chips  are  now  avoided 
quite  as  certainly  by  taking  proper  care  to  have  sufficient  liquor 
in  the  digester.  Some  form  of  strainer  is  always  necessary  in  the 
top  of  the  digester  to  prevent  the  pulp  from  being  carried  into  the 
blow-off  pipe.  Sometimes  a  hemisphere  of  hard  lead  is  burned 
to  the  manhole  plate  around  the  entrance  to  the  blow-off;  while 
often  instead  of  this  a  larger  hemisphere  rests  on  a  ledge  in  the 
neck  of  the  digester.  In  either  case  the  metal  of  the  strainer  is 
punched  with  numerous  ^-inch  holes. 

Much  stress  was  formerly  laid  upon  the  importance  of  thorough 
circulation  of  the  liquor  during  boiling,  and  various  devices  have 
been  employed  to  secure  this  circulation ;  among  them  may  be 
mentioned  the  injector  placed  in  a  pipe  leading  from  the  bottom 
of  the  digester  under  a  perforated  false  bottom,  and  discharging 
through  the  manhole  plate  at  the  top.  When  the  injector  is 
working  properly,  the  liquor  is  drawn  from  the  bottom  of  the 
digester,  carried  round  through  the  pipe,  and  discharged  on  top 
of  the  pulp.  We  have  worked  digesters  fitted  with  this  appliance 
for  several .  months  without  perceiving  the  slightest  benefit  from 
its  use,  and  are  satisfied  that  no  advantage  offsetting  the  additional 
expense  is  to  be  derived  from  any  of  the  methods  for  securing 
circulation,  such  as  outside  pumps  or  vomiting  pipes  in  the  interior 
of  the  digester.  No  such  devices  are  now,  in  fact,  used  in  this 
process. 

Although  it  is,  of  course,  desirable  to  discharge  the  digester  as 
soon  as  possible  after  the  reduction  of  the  wood  has  been  com- 
pleted, there  is  no  danger  of  injuring  the  pulp  through  keeping 
it  too  long  in  the  digester,  provided  always  that  the  liquor  is  of 
proper  strength,  and  that  it  has  not  been  unduly  weakened  by 
blowing  off.  We  have  in  several  cases,  where,  owing  to  a  break- 
down in  another  portion  of  the  mill,  it  was  inconvenient  to  blow 
a  digester  off  at  once,  kept  the  digester  under  pressure  for  twenty- 
four  hours  or  more  after  the  cooking  was  completed,  and  in  no 
case  has  the  pulp  been  injured  in  the  least,  either  as  regards 
strength  or  color. 

With  a  working  pressure  of  75  Ibs.  and  liquor  carrying  3.50  per 
cent,  of  sulphurous  acid,  the  best  results  are  obtained  when  four 
or  five  hours  are  taken  in  reaching  full  pressure,  and  sixteen  hours 
for  the  entire  cook.  There  is  considerable  difference  of  opinion 


THJS  SULPHITE  PROCESS.  255 

regarding  the  relative  merits  of  the  systems  using  high  pressure 
for  a  short  time,  and  those  working  at  lower  pressures  for  a  longer 
time.  In  our  opinion  the  disintegration  of  the  wood  is  more  com- 
plete, and  the  pulp  softer  and  of  purer  quality,  when  the  boiling 
is  conducted  at  high  temperatures,  provided  that  the  liquor  is  suffi- 
ciently strong  to  prevent  burning.  The  use  of  strong  liquor 
involves,  however,  more  gas  pressure,  so  that  unless  the  boiling 
is  carried  on  by  the  thermometer  the  temperatures  reached  may 
run  lower  than  if  a  weaker  liquor  is  employed ;  and  the  pulp  will 
consequently  be  harsh  and  imperfectly  cooked,  and  will  require, 
if  subsequently  bleached,  a  large  proportion  of  bleaching  powder. 

It  would  seem,  on  theoretical  grounds,  more  desirable  to  heat  the 
digester  either  by  a  steam  jacket^  or  by  coils  of  pipe,  than  with  live 
steam,  since  in  the  latter  case  the  liquor  necessarily  becomes  much 
diluted.  This  condensed  water  introduces  an  uncertain  factor  in 
the  working  of  the  process,  since  its  amount  will  necessarily  vary 
from  day  to  day  with  the  temperature  and  dryness  of  the  steam, 
and  the  temperature  of  the  air  outside.  With  proper  care,  how- 
ever, and  especially  if  a  non-conducting  jacket  is  employed,  these 
objections  are  not  serious,  and  the  greater  convenience  of  the  live 
steam  has  caused  its  general  adoption.  A  good  jacket  of  this 
description  is  made  by  plastering  the  digester  over  with  clay  mixed 
with  cocoanut  fibre. 

The  amount  of  condensed  water  formed  in  a  lead-lined  digester 
of  moderate  size,  or  about  6J  feet  in  diameter,  during  a  single 
boiling  is  much  larger  than  it  would  be  at  first  sight  supposed. 
Under  ordinary  conditions,  in  summer,  we  have  found  this  amount 
to  be  as  large  as  1000  gallons,  and  during  the  cold  winter  of  the 
Northwest  we  have  frequently  known  the  amount  to  be  so  great 
as  completely  to  fill  the  digester  In  &ueh  cases  it  is,  of  course, 
impossible  to  heat  the  liquor  by  airy  further  addition  of  steam,  and 
the  cook  can  only  be  completed  by  allowing  the  pressure  to  fall 
until  most  of  the  dilute  liquor  can  be  rtm  off,  and  then  making  a 
fresh  start  with  new  liquor.  The  advantage  of  the  thermometer 
is  very  apparent  in  a  case  like  this,  as  when  the  digester  is  filled 
with  water  the  pressure  remains  .at  the  proper  point,  and  the  true 
condition  of  affairs  is  only  shown  by  the  steady  dropping  of  the 
temperature.  In  the  case  mentioned  above  the  mill  was  practically 
heated  by  radiation  from  the  digesters,  and  the  trouble  was  over- 
come by  boxing  them  in  so  that  they  were  shut  off  from  the  rest 


256  THE  CHEMISTRY  OF  PAPER-MAKING. 

of  the  mill.  If  the  liquor  has  been  unduly  weakened  by  the  con- 
densed water,  although  not  necessarily  to  the  point  indicated 
above,  the  fact  may  usually  be  ascertained  by  the  raw  and  chippy 
condition  of  the  pulp. 

The  introduction  of  cement  linings  has  practically  eliminated 
the  difficulties  due  to  condensed  water  and  loss  of  heat  through 
the  digester  wall.  Considerable  condensed  water  is,  of  course, 
still  formed,  and  there  is  still  some  loss  of  heat  by  radiation,  but 
both  factors  are  by  these  linings  greatly  reduced  in  value,  and, 
which  is  of  far  more  importance,  they  are  made  to  have  a  nearly 
uniform  value  for  each  cook. 

It  is  desirable  to  have  the  connections  between  the  generating 
boilers  and  the  digesters  as  short  as  possible,  to  avoid  loss  from 
condensation  of  steam  and  reduction  of  the  steam  pressure.  Where 
a  number  of  digesters  are  fed  from  the  same  steam-pipe,  its  area 
should  be  several  times  greater  than  that  of  all  the  pipes  leading 
from  it,  or  else,  as  our  tests  in  practice  have  shown,  the  digesters 
at  the  farther  end  of  the  pipe  will  receive  steam  under  considerably 
lower  pressure  than  those  nearer  the  boilers.  All  steam-pipes 
should  be  well  trapped,  and  steam  as  dry  as  possible  should  be 
used  for  cooking,  in  order  to  keep  down  condensed  water. 

The  steam-pipe  leading  into  the  digester  is  often  led  up  to  the 
top  of  the  digester,  and'  then  back  and  into  the  bottom,  to  form  a 
trap,  and  is  fitted  with  two  check-valves, — one  placed  on  the 
horizontal  arm  of  the  steam-pipe,  near  the  digester,  and  the  other 
on  the  vertical  arm  of  the  trap.  The  object  of  these  precautions 
is  to  prevent  any  of  the  liquor  from  being  forced  from  the  digester 
into  the  generating  boilers,  as  may  easily  happen  if  the  gas  pressure 
is  considerable  in  the  digester,  when,  for  any  cause,  the  steam 
pressure  has  been  allowed  to  fall  in  the  boilers.  Considerable 
danger  to  the  boilers  may  be  apprehended,  if  the  liquor  finds  its 
way  into  them,  as  the  acid  rapidly  attacks  the  iron,  while  the 
sulphite  of  lime  is  likely  to  form  scale. 

Boiling  by  the  Mitscherlich  Process.  —  After  the  digester  has 
been  packed  with  chips  or  blocks,  which  are  levelled  off,  so  that 
none  shall  be  uncovered  by  the  liquor,  wet  steam  is  admitted  into 
the  boiler,  and  the  steaming  continued  from  eight  to  twelve  hours. 
Care  is  taken  to  avoid  any  pressure  in  the  boiler,  as,  if  the  tem- 
perature is  allowed  to  rise  above  102°,  the  wood  is  in  danger  of 
burning.  The  water,  condensing,  flows  away  as  brown  liquor. 


THE  SULPHITE  PROCESS.  257 

The  object  of  the  steaming,  and  subsequent  admission  of  cold 
liquor,  is  to  bring  the  liquor,  at  the  start,  well  into  the  pores  of 
the  wood,  so  as  to  prevent  floating  and  burning. 

The  liquor  used  stands  from  5°-7°  Be*. ;  and  after  the  steaming 
is  finished,  this  is  drawn  into  the  digester  by  the  partial  vacuum 
which  forms  as  the  digester  cools,  and  more  rapidly  as  the  cold 
liquor  is  injected.  The  flow  of  liquor  is  continued  until  it  comes 
to  within  about  15  inches  of  the  top  of  the  digester.  Steam  is 
then  admitted  into  the  lead  coils,  and  the  temperature  of  the 
digester  contents  is  brought  to  110°  C.  in  as  short  a  time  as  may 
be,  although,  on  account  of  the  large  size  of  the  digester,  this  may 
require  twelve  hours  or  more.  This  temperature  is  maintained  for 
about  twelve  hours,  and  is  then  gradually  increased  to  117°-120°  C. 
The  pressure  on  the  digester  should,  according  to  Mitscherlich, 
be  at  no  time  allowed  to  exceed  45  Ibs.  The  quantity  of  gas 
blown  off,  and  the  length  of  the  boiling  operation,  is  governed  by 
tests  made  upon  samples  of  liquor  taken  from  the  digester.  For 
these  tests,  tubes  are  used  which  are  200  mm.  long,  closed  at  one 
end,  and  graduated  into  -j,  T*j,  ^,  and  -fa  of  their  length.  A 
mixture  of  strong  ammonia  and  water  in  equal  parts  is  poured 
into  the  tube  up  to  the  •£%  mark,  and  the  balance  of  the  tube  is 
filled  with  liquor,  and  the  tube  well  shaken* 

All  the  bisulphite  of  lime  present  is  thus  converted  into  mono- 
sulphite,  and  precipitated ;  and  from  the  volume  and  character 
of  precipitate,  conclusions  as  to  the  progress  of  the  operation  are 
drawn.  The  higher  the  precipitate  stands  in  the  tube,  the  more 
bisulphite  there  is  in  the  liquor.  The  liquor  grows  darker  as  the 
cooking  is  prolonged,  and  the  precipitate,  which  is  at  first  light 
and  fine,  becomes  coarse,  and  settles  rapidly.  When,  after  a  few 
moments'  standing,  the  precipitate  fills  only  ^  the  length  of  the 
tube,  gas  is  blown  off  from  the  digester  in  moderate  quantity,  and 
at  ^j  the  amount  blown  off  is  increased  sufficiently  to  bring  a  tem- 
perature down  to  110°.  The  completion  of  the  cook  is  indicated 
when  the  precipitate  sinks  to  ^. 

The  course  of  a  Jlitscherlich  cook  and  the  very  long  time 
required  to  carry  it  through  are  well  brought  out  in  the  following 
tables  from  Schubert.1  It  will  be  noticed  that  the  total  time  of 
boiling  is  reckoned  from  the  commencement  of  what  is  taken  as 
the  first  stage  of  the  pulping  operation ;  i.e.  from  the  time  of  reach - 
1  Die  Cellulosefabrikation. 


258 


THE  CHEMISTRY  OF 


ing  108°.  For  any  comparison  with  a  quick  cook  the  time  taken 
to  reach  this  temperature  should,  of  course,  be  added  to  the  so- 
called  total  time  as  given. 

BOILING  No.  207. — Ix  A  HORIZONTAL  DIGESTER. 


April  23. 

11.30  A.M. 
8          P.M. 

Pressure  in  atmosphere*. 

0.00 
0.60 

Temperature,  °C. 

45 
72 

April  24. 

1          A.M. 

6 

0.75 
1.00 

85 
96 

11.30 

100 

105 

2.30  P.M. 

1.75 

108 

6,30 

2.00 

112 

April  25. 

1         A.M. 

6 

2.50 
2.80 

115 
116*5 

9 

3.00 

119 

12         M. 

2.80 

120 

3          P.M. 

2.25 

119 

10 

2.10 

118 

Remark*. 

Filled  April  22,  from  1.30  to  11  P.M.,  88  cubic  metres  wood  in  disks, 
9  cubic  metres  wood  in  chips. 

Steamed  from  midnight  to  8  A.M.  April  23. 
Acid  of  5°  B<*.  run  in  from  8  to  11.30  A.M. 

After  27     hours  temperature  reached  108°  \     9.  -  hours 


10.    hours, 


v 

After  48.5  hours  temperature  reached  116° )  ) 
After  58.5  hours  boiling  finished  at  118°         )"  _ 

Total  time  of  boiling 31.5  hours. 

Highest  pressure,  3  atmospheres.      Highest  temperature.  120°. 
Cellulose,  very  fair. 

20.  —  Ix  A  HORIZONTAL  DIGESTER. 


BOILING  Ko. 

Junf,  2. 

6  A.M. 

11 

4  P.M. 

12 

June  3. 

.5  A.M. 

7 

12  M. 

10  P.M. 

June  4. 

8  A.M. 

1    P.JVl. 

Pressure  in  atmosphere*, 

0.0 
0.5 
1.0 
2.0 
2.7 
3.0 
3.0 
3.0 
3.0 
S.O 


Temperature,   0. 

40 

73 

97 
108 
116 
.118 
118 
118 
118 
118 


THE  SULPHITE  PROCESS. 


259 


Remarks. 

Filled  June  1,  1  P.M.  to  3.30  A.M.,  with  60  cubic  metres  of  wood. 

Steamed  from  3.30  A.M.  to  3.30  P.M.  June  2. 

Liquor  of  5.5°  Be.  pumped  in  from  4.30  P.M.  to. 6  A.M. 

After  18  hours  reached  108°  >        7 

After  25  hours  reached  118°  > 

After  55  hours  finished  at  118°  >  ^ 

Total  time  of  boiling   .     ,37  hours. 
Cellulose,  good. 

BOILING  No.  101.  —  Ix  AN  UPRIGHT  DIGESTER. 


Aus.  2.   4.30  P.M. 


hours. 


Aug.  3.   9 

11 

1 

3 

6 

Aug.  4.   6 

8 

10 

12 

2 

4 

6 


A.M. 


P.M. 


A.M. 


M. 

P.M. 


Aug. 


5.   6      A.M. 
7.30 


Presume  in  atmospheres. 
At  top..       At  bottom. 

0.0 

0.0 

0.3 

0.3 

0.4 

0.3 

1.0 

0.4 

1.2 

1.0 

1.3 

1.2 

2.4 

2.3 

2.4 

2.3 

3.0 

2.4 

3.0 

2.4 

3.0 

2.4 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

3.0 

Temperature,  °C. 
At  top.    At  bottom. 

30 

40 

87 

87 

89 

89 

96 

95 

102 

99 

106 

103 

120 

115 

122 

11G 

122 

117 

122 

117 

122 

117 

122 

117 

122 

117 

122 

117 

122 

117 

Remarks. 

Filled  Aug.  1,  P.M.,  with  wood  of  mixed  sizes. 
Steamed  Aug.  2,  from  1  A.M.  to  1  P.M. 
Liquor  of  5-V  Be.  pumped  in  from  2.15  to  4.15  P.M. 
After  28  hours  reached  108°  ) 
After  30  hours  reached  114°  V-       9  hours. 
After  37  kours  reached  118°  )  ) 
After  63  hours  finished  at  118°  )  _ 

Total  time  of  boiling  .     .     35  hours. 

Emptied  on  morning  of  Aug.  6. 
Cellulose,  fine. 

This  boiler  was  4  metres  diameter,  and  9  metres  high,  and  contained 
60  cubic  metres  of  wood  in  disks. 


260  THE  CHEMISTRY  OF  PAPER-MAKING. 

It  was  formerly  considered  established  as  a  fundamental  law  in 
this  process,  that  the  pressure  in  the  digester  should  never  exceed 
45  Ibs.,  and  if  a  temperature  of  114°  was  reached,  gas  was  at  once 
blown  off.  Now,  however,  the  boiling  operation  is  shortened  as 
much  as  possible,  and  by  bringing  the  pressure  from  3.4  to  3.5 
atmospheres,  and  the  temperature  to  120°  C.,  no  evil  results  are 
experienced,  and  the  time  is  cut  from  seventy-five  to  eighty-five 
hours  down  to  fifty-eight  hours  or  less ;  of  which  only  thirty-two 
are  properly  consumed  by  the  boiling.  It  is  usual  in  Germany 
to  hold  the  pressure  up  to  the  very  end,  and  in  this  Country  it  is 
often  slowly  and  regularly  raised  during  the  last  hours. 

The  body  of  pulp  contained  in  one  of  these  digesters  is  so  great 
that  there  is  danger  of  burning  as  soon  as  the  liquor  has  been  run 
off,  and  it  is  therefore  customary  to  let  in  cold  water  and  wash  the 
pulp  two  or  three  times  in  the  digester.  Even  then  the  pulp  is 
still  so  hot  that  all  manholes  are  opened,  and  holes  punched  up 
through  the  stuff  to  create  a  draft  of  air.  The  pulp  is  finally 
shovelled  out  of  the  digester. 

The  actual  time  consumed  by  one  cook  from  the  time  of  filling  to 
that  of  blowing  off  is,  as  shown  by  the  tables  previously  given :  — 

No.    20 :     .     80J  hours. 

101 '  ...    87       « 

207    .....    .    .    .    .    .    72       « 

In  addition  to  this  the  time  required  for  discharging  the  liquor, 
cooling,  washing,  emptying,  and  for  repairs,  is  at  least  from 
eighteen  to  twenty-four  hours,  making  a  grand  total  of  ninety  to 
one  hundred  hours,  and  allowing  only  seven  or  eight  cooks  per 
month  at  best. 

It  is  customary  after  each  boiling  by  the  Mitscherlich  process 
to  inspect  the  digester  for  the  location  of  any  leaks  or  weak  places 
in  the  cement.  Such  affected  portions  ma}r,  in  most  cases,  be 
quickly  repaired  by  cutting  out  the  cement  and  repointing.  A 
considerable  incrustation  of  sulphite  of  lime  forms  on  the  lead 
coils  during  each  cook,  and  is  usually  removed  by  rapping  with 
a  mallet.  This  is  likely  to  dent  the  pipes,  and  a  better  way  is  to 
use  a  scraper.  Any  leaks  in  the  coils  cause  trouble  through  depo- 
sition of  sulphite  within  the  pipe.  A  stream  of  weak  hydrochloric 
acid  sent  through  the  coil  will  remove  this,  unless  the  deposit  at 
any  point  is  sufficient  to  close  the  coils. 


THE  SULPHITE  PROCESS.  261 

The  standard  Mitscherlich  digesters  with  40  x  14  shell  carry 
from  22  to  25  cords  of  wood  at  a  charge,  and  yield  from  10  to  14 
tons  of  fibre  at  a  boiling.  So  much  time  is  lost,  however,  in  wash- 
ing, emptying,  and  charging  up,  that  these  digesters  rarely  show 
in  continuous  working  a  better  average  output  than  8000  Ibs.  per 
twenty-four  hours. 

Leaving  breakdowns  out  of  account,  there  is  hardly  an  excuse 
when  good  pulp  has  once  been  made  by  any  process,  and  the  con- 
ditions governing  that  boiling  are  fully  known,  for  failure  to 
produce  pulp  of  similar  quality,  since  the  same  conditions  must 
invariably  produce  the  same  results.  The  trouble  usually  arises 
from  imperfect  knowledge  of  the  conditions,  and  every  care  should 
be  taken  to  learn  and  govern  them  as  accurately  as  possible.  A 
few  of  the  first  importance  may  be  pointed  out.  It  is  absolutely 
necessary,  in  order  to  obtain  pulp  of  uniform  quality,  to  use  with 
the  same  kind  of  wood  liquor  of  good  and  always  uniform  quality. 
There  should  be  no  variation  in  the  time  taken  for  reaching  pres- 
sure, or  in  that  during  which  the  pressure  is  maintained ;  the  con- 
densed water  and  consequent  dilution  of  the  liquor  should  be  kept 
at  a  definite  and  regular  amount  by  preventing  radiation  as  much 
as  possible,  and  by  using  steam  of  uniform  pressure.  The  amount 
of  gas  blown  off,  if  any,  must  also  be  controlled,  and  should  not 
vary  from  day  to  day.  Failure  to  make  good  pulp  usually  results 
from  disregard  of  these  conditions,  which  can  all  be  readily  con- 
trolled. There  are  certain  others  which  necessarily  introduce 
some  uncertainty  in  the  process ;  one  of  these  is  the  variation  in 
the  condition  and  moisture  of  the  wood  used. 

Recovery  of  Gas.  —  At  the  time  of  the  present  writing,  1893, 
no  attempt  is  made  in  any  mill  in  this  country  other  than  those 
working  the  Mitscherlich  process,  to  recover  the  large  proportion 
of  sulphurous  acid  which  is  blown  off  previous  to  the  dumping  of 
the  digester,  although  the  gas  may  be  utilized  by  a  very  simple 
apparatus,  which  is  regularly  in  use  abroad.  The  best  form  of 
apparatus  for  this  purpose  consists  of  a  tower  filled  with  flints  or 
broken  brick.  The  gas  and  steam  from  the  blow-off  are  admitted 
to  the  tower  under  the  false  bottom,  while  a  shower  of  water  is 
kept  up  at  the  top  of  the  tower.  This  water,  as  it  passes  down 
the  tower,  absorbs  the  gas  and  is  somewhat  heated  by  the  steam ; 
as  it  progresses,  more  gas  is  absorbed  until  the  water  becomes 
saturated,  while  through  condensation  of  the  steam  the  tempera- 


262 


TffEl  V3£MI8T3r  OF  PAPEit-MAEING 


bure  of  the  water  is  soon  raised  to  a  point  where  it  can  no  longer 
hold  the  gas  in  solution.  This  liberated  gas,  passing  upward  with 
that  still  coming  from  the  digester,  soon  increases  in  quantity  to 
such  an  extent  that  the  water  falling  down  is  not  sufficient  to  dis- 
solve it,  and  there  is  constantly  delivered  from  the  top  of  the 
tower  a  stream  of  pure  gas,  while  from  the  bottom  of  the  tower 
hot  water  is  drawn,  to  be  used  in  washing  or  for  other  purposes. 
The  amount  of  sulphur  thus  saved  is  usually  not  less  than  20  per 
cent. 

ID  the  Mitscherlich  process  the  waste  gases  are  blown  through 
a  pipe  leading  from  one  of  the  upper  manhole  plates  to  a  lead  coil 
immersed  in  water.  All  the  digesters  are  connected  with  this 
coil,  which  in  turn  is  connected  to  one  of  the  towers.  The  steam 
carried  over  by  the  gas  is  condensed  and  the  pure  gas  passes  on 
into  the  tower.  Such  recovered  gas,  being  undiluted  with  atmos- 
pheric nitrogen,  is  better  suited  for  the  preparation  of  strong 
liquors  than  the  original  furnace  gas.  It  may  be  made  to  yield 
a  liquor  standing  12°  Be*. 

Dr.  Kellner  has  also  used  the  coil  and  tower  for  recovering  the 
gas  blown  off  during  the  cook.  For  recovering  that  discharged 


FIG.  00.  —  KELLNEH  RECOVERY  AFPVBATUB. 

with  the  liquor  after  the  cook  is  finished,  he  has  employed  the 
apparatus  shown  in  a  diagrammatic  way  in  Fig.  60. 

At  Northfleet,  England,  the  simple  plan  is  adopted  of  blowing 
off  the  gas  into  a  six-inch  pipe  laid  on  the  ground,  and  lea'ding  to 


TUK  SULPHITE  PROCESS. 


fin 

•—-  •" 

[In. 

the  tower.     The  pipe  has  a  pitch  toward  the  mill,  and  the  con- 
densed water  flows  back,  while  the  gas  goes  forward. 

Various  means  are  adopted  in  the  different  mills  to  get  the  pulp 
out  of  the  digester.  That  which  now  finds  most  favor  is  to  blow  it 
out  under  a  pressure  of  about  30  Ibs.  The  digester  is  thus  emptied 
perfectly  clean  in  a  few  seconds,  and  the  pulp  is  so  well  disin- 
tegrated that  no  subsequent  treatment  in  the  beating  engine  is 
necessary  to  fit  it  for  the  market.  It  is  urged  against  this  method, 
that  there  is  danger  of  breaking  up  the  knots  and  uncooked  chips, 
thus  causing  slave  and  dirt,  while  at  the  same  time  unnecessarily 
straining  the  digester.  The  danger  to  the  digester  is  practically 
nothing,  arid  there  is  certainly  less  danger  of  breaking  up  the 
knots  in  this  way  than  by  running  the  pulp  for  several  hours 
under  the  roll  of  the  beating  engine.  Where  the  pulp  is  simply 
allowed  to  run  out  of  the  digester,  considerable  time  is  lost,  and  a 
large  amount  of  water 
must  be  pumped  into  the 
digester  before  the  pulp 
is  all  out.  This  water  is 
in  most  cases  cold,  and 
the  sudden  admission  of 
it  in  so  large  a  volume 
strains  the  lead  severely. 
The  practice  of  washing 
the  pulp  in  the  digester 
before  discharging  must 
be  condemned,  as  the 
whole  product  of  the  mill 
is  curtailed,  while  an 
expensive  piece  of  appa- 
ratus is  employed  in 
doing  work  which  can 
be  much  more  efficiently 
done  in  apparatus  costing 
only  a  fraction  as  much. 

The     Mitscherlich 

stumping  mill,  as  used  in 

0  ,,t      .       .  .  Era.  61.  —  aUTSCHJEBLiCH  STAMJK  MILL. 

foreign  mills,  is  shown  in 

side    view   and   sections   in   Figs.    61  and    0*2;    on    about  seven 
of  the  frames  A  is  laid  or  carried  the  shaft  #,  bearing  numer- 


264 


THE  CHEMISTRY  OF  PAPER-MAKING. 


ous  cams ;  the  shaft  turns  about  ten  times  in  a  minute ;  there 
are  two  stout  beams,  J)  D'  and  (7  <7',  which  hold  the  frames 
together,  and  also  serve  as  guides  for  about  60  stamps,  which 
reach  nearly  to  the  bottom  of  the  stamping  trough  E\  the  trough 
is  15  metres  long,  and  rises  about  0.6  metres  in  this  distance ;  tho 
stamps  are  lifted  by  teeth,  which  engage  the  cams ;  the  teeth  of  the 
three  or  four  adjacent  stamps  are  arranged  as  in  Fig.  61,  so  that 
these  stamps,  instead  of  falling  together,  follow  each  other.  This 

action,  and  the  flow  of 
water  through  the  trough, 
passes  the  stuff  along ; 
the  action  of  the  mill  is 
largely  a  rubbing  ono,  on 
account  of  the  different 
motion  of  the  adjacent 
stamps :  in  some  mills 
the  wood  is  broken  up  by 
a  heavier  stamping  ma- 
chine before  boiling.  This 
saves  subsequent  stamp- 
ing, and  makes  somewhat 
shorter  cooks  possible. 
The  stuff  is  also  worked 
under  edged  runners,  and 
these  are  commonly  em- 
ployed to  reduce  knots 
and  chips  to  a  pulp  suit- 
able for  coarse  papers.  The  unreduced  remainder  is  roughly 
screened  from  the  fibre  by  rotating  drums  similar  to  rag  dusters. 

If  the  digester  has  been  blown  off  into  a  drainer,  the  most  con- 
venient method  of  washing  the  pulp  is  to  flood  it  two  or  three  times 
with  water.  It  should  be  observed,  however,  that  the  pulp  forms 
in  itself  a  most  efficient  filter,  so  that,  in  case  the  wash  water 
carries  any  considerable  amount  of  suspended  organic  matter,  this 
will  be  fixed  upon  the  pulp,  and  more  will  be  lost  than  gained  by 
prolonging  the  washing.  In  some  mills  the  washed  pulp  is  trans- 
ferred, with  little  labor,  from  the  drainer  to  the  chest,  in  readiness 
for  the  wet  machine,  by  directing  a  powerful  stream  of  water 
against  the  mass  of  pulp  in  the  drainer,  and  washing  it  out  in  a 
sluiceway,  from  which  a  pump  throws  it  over  into  the  chest.  In 


FIG.  62.  —  MITSCHEKLICH  STAMP  MILL. 


THE  SULPHITE  PROCESS.  265 

other  mills  the  drainers  themselves  consist  merely  of  large  chests 
with  a  wooden  chimney  for  the  escape  of  gas,  and  an  agitator. 
In  this  case  no  attempt  is  made  to  wash  the  pulp  in  the  drainer, 
but  it  is  pumped  direct  into  the  washing-machine.  The  drainers 
should  always  be  protected  before  blowing  off,  by  a  foot  or  two  of 
water  let  into  the  bottom,  to  break  the  force  of  the  pulp  as  it 
strikes  the  drainer  bottom. 

The  washing-machine  just  referred  to,  although  not  in  common 
use,  is  very  efficient,  and  consists  merely  of  a  trough  provided  with 
three  or  four  washing  cylinders,  with  a  corresponding  number  of 
back-falls.  The  first  cylinder  removes  a  large ,  proportion  of  the 
water  from  the  pulp,  and,  as  the  pulp  is  thrown  over  the  back-fall, 
it  meets  a  copious  stream  of  fresh  water  from  a  pipe  behind  the 
washer;  and  the  same  operation  is  repeated  as  many  times  as 
there  are  washers  while  the  pump  passes  along  the  trough. 

Washing  in  the  engine  is  conducted  after  the  ordinary  method, 
which  is  too  well  known  to  require  comment  further  than  to  point 
out  the  great  danger  of  breaking  up  chips  and  forming  shive, 
unless  the  engine  roll  is  well  raised. 

Thorough  washing,  although  always  desirable,  must  be  insisted 
upon  wherever  the  pulp  is  to  be  bleached;  for  monosulphite  of 
lime  requires  a  large  amount  of  water  for  its  complete  removal, 
and,  if  present  in  the  pulp,  may  greatly  increase  the  consumption 
of  bleaching  powder,  as  it  is  one  of  the  most  efficient  antichlors  in 
use.  When  present  in  excessive  quantity,  it  may  be  best  removed, 
and  the  pulp  considerably  benefited,  by  washing  with  dilute 
hydrochloric  acid. 

The  further  handling  of  the  unbleached  pulp  belongs  to  the 
practical  paper-maker  rather  than  to  the  chemist. 

The  bleaching  of  this  pulp  and  of  the  other  paper-making  fibres 
will  be  considered  in  a  separate  chapter ;  but  we  may  here  point 
out  that  it  is  desirable,  before  bleaching  sulphite  pulp,  to  remove 
all  large  shives  by  thorough  screening,  as,  in  the  bleaching 
process,  these  shives  are  broken  up  into  smaller  ones,  which  it  is 
very  difficult  to  remove,  and  which  injure  the  appearance  of  the 
paper,  though  they  may  readily  escape  notice  in  the  wet  pulp. 

Well  cooked  and  bleached  sulphite  pulp  should  be  soft,  strong, 
and  of  pure  color;  the  frequent  failures  to  meet  these  require- 
ments are  due  either  to  imperfect  cooking,  which  leaves  the  pulp 
harsh  and  hard,  or  to  defects  in  the  method  of  bleaching,  which, 


2G6  THE  CHEMISTRY  OF  PAPER-MAKING. 


especially  when  hot  bleach  is  used,  may  lower  the  color  and  injure 
the  strength,  by  chlorination  and  oxidation  of  the  fibre. 

The  conditions  which  affect  unfavorably  the  quality  of  the 
finished  pulp  have  been  already  pointed  out  in  some  instances,  but 
may  be  conveniently  considered  together.  Poor  color  may  be  due 
to  imperfect  cooking,  which  has  failed  to  remove  the  necessary 
amount  of  iricrusting  matter,  or  it  may  be  caused  by  unduly 
weakening  the  liquor  by  blowing  off  too  much  gas.  If  the  proper 
cooking  temperatures  are  maintained  the  color  of  the  pulp  improves 
as  more  gas  is  present  in  the  liquor.  Raw  pulp  is,  of  course,  due 
either  to  insufficient  time  or  too  low  a  temperature,  and  the  latter 
may  be  caused  by  working  with  too  strong  a  liquor,  in  which  case 
the  large  amount  of  gas  pressure  makes  it  difficult  to  bring  up  the 
temperature  to  the  proper  point ;  or,  if  very  wet  steam  is  used,  or 
if  the  digest-era  radiate  an  undue  amount  of  heat,  the  quantity  of 
condensed  water  formed  in  the  quick  cooking  digesters  may  be 
sufficient  to  fill  the  digester  and  prevent  the  admission  of  the 
necessary  steam.  Black  chips  similar  to  charcoal  are  found  in  the 
pulp  when  any  of  the  wood  has  remained  uncovered  by  the  liquor, 
and  ft  simple  remedy  for  them  is  found  in  more  liquor  or  less  wood. 
If  the  whole  body  of  the  pulp  is  burned,  it  means  that  the  liquor 
was  too  weak  for  the  temperatures  carried.  If  too  much  gas  is 
blown  off  the  liquor  may  be  weakened  during  the  boiling  to  an 
extent  which  permits  the  pulp  to  burn,  and  burning  is  especially 
likely  to  occur  if  the  liquor  is  drained  oft'  and  the  cooked  pulp 
allowed  to  remain  in  the  hot  digester  for  more  than  a  few  moments 
before  water  is  run  in.  After  the  pulp  has  been  cooked,  it  may  be 
kept  in  the  digester  under  pressure  for  almost  any  length  of  time, 
if  the  liquor  contains  a  good  supply  of  gas.  Chips  which  are  well 
cooked  upon  tho  outside,  but  which  have  a  hard,  red  or  brown 
centre,  are  formed  when  the  temperature  has  been  raised  so  rapidly 
that  the  liquor  did  not  liave  time  to  penetrate  into  and  protect  the 
interior  of  the  wood  before  the  temperature  was  high  enough  to 
burn  such  unprotected  portions.  Any  great  precipitation  of  mono- 
sulphite  of  lime  in  the  pulp,  where  it  makes  trouble  by  causing 
specks,  is  due  either  to  the  use  of  a  liquor  containing  little  or  no 
free  sulphurous  acid  above  that  needed  to  form  bisulphite,  or  else 
to  the  formation  of  such  a  liquor  in  the  digester,  by  blowing  off  too 
much  ga-s.  The  objectionable  red  coloration  which  some  sulphite 
pulp  takes  on  after  washing  is  the  result,  so  nearly  as  we  can 


THE  SULPHITE  PROCESS.  267 

determine,  of  the  oxidation  of  portions  of  incrusting  matter,  which 
have  not  been  removed  during  cooking,  and  can  generally  be 
avoided  when  the  cooking  is  made  more  thorough.  Strangely 
enough,  however,  the  pulp  from  poplar  wood,  which  is  very  easily 
reduced  by  the  sulphite  process,  frequently  develops  this  color  in  a 
way  much  more  marked  than  spruce.  The  color  is  a  purer  one, 
and  often  approaches  a  delicate  pink.  Dirt  and  specks,  of  course, 
find  their  way  into  the  pulp  from  various  sources.  Fragments  of 
bark  which  have  not  been  removed  in  the  preparation  of  the  wood, 
fragments  of  knots  which  have  been  broken  up  by  the  boring 
machine  or  in  the  treatment  of  the  pulp  subsequent  to  boiling,  and 
shives  formed  by  the  breaking  up  of  uncooked  or  partially  burned 
chips,  are  the  most  common  causes  of  dirt,  but  lumps  of  mono- 
sulphide  left  by  imperfect  washing,  iron  scale  from  water  pipes, 
sulphide  of  copper  from  pipes  and  fittings,  coal,  black  sand,  arid 
fragments  of  brick,  all  frequently  find  their  way  into  the  product. 

The  unbleached  sulphite  fibre,  owing  to  the  numerous  systems 
employed  for  its  production,  shows  even  wider  variation  in  quality 
than  the  bleached  fibre.  As  found  in  the  market,  it  may  be  either 
a  harsh  and  somewhat  transparent  very  strong  fibre,  or  one  nearly 
as  soft  and  white  as  the  bleached  pulp.  Spruce  is  the  wood  most 
preferred  in  this  country  for  making  this  pulp :  abroad,  the  Swedish 
fir  and  pine  are  both  used,  as  well  as  spruce,  and  several  of  our 
common  woods  readily  yield  a  strong  fibre.  We  give  below  a  very 
complete  analysis,  made  by  ourselves,  of  a  sample  of  sulphite  fibre 
made  from  spruce  by  the  Mitscherlich  process. 

ANALYSIS  OF  UXBLK ACHED  SULPHITE  PULP. 

(Mits<:h crlif.h   Process. ) 

Per  cent. 

Moisture,  loss  at  100°  C 9.000 

Extractive    organic  matter,   soluble   in   very  dilute 

hydrochloric  acid     . .     .     .  0.516 

Extractive   organic   matter,   soluble   in    very    dilute 

alkali 1.505 

Kesin 0.060 

Cellulose ,  80.800 

Mineral  matter: 

«.   Removable  by  very  dilute  acid     .     .     .     .     .'  .  0.758 

b.   Not  removable  by  very  dilute  acid  .     ...     .  0.742 

Lignin,  by  difference ,    .    .     .  6.6 19 

100.000 


268 


THE  CHEMISTRY  OF  PAPER-MAKING. 


Mineral  matter : 

«.    contains —  Percent. 

Silica  (SiO,) 0.009 

Iron  sesquioxide  (Fe2O8) 0.031 

Sulphate  of  lime  (GaS04) 0.333 

Sulphite  of  lime  (CaS08) 0.004 

Carbonate  of  lime  (CaCO3) 0.261 

Carbonate  of  magnesia  (MgC08) 0.025 

Carbonate  of  soda  (Na^CO,) 0.095 

0.758 

b.   Ash  of  washed  pulp  contains  —  pw  c«nt. 

Silicate  of  soda  (Na2Si03)     .........  0.042 

Iron  sesquioxide  (Fe3O8) °.010 

Sulphate  of  lime  (CaSO4)      . 0,158 

Carbonate  of  lime  (CaCOa) 0.050 

Carbonate  of  magnesia  (MgC08) .  .  0.029 

Carbonate  of  soda  (Na^COg) 0.453 

0.742 

Total  mineral  matter  in  sample 1.500 

Oxygen  and  carbonic  acid  lost    on  burning  (calcu- 
lated)      .'    •  - 0.398 

Calculated  ash  to  be  obtained  from  sample    ....       1.102 
Actual  ash  obtained  by  burning 1.084 

Our  analyses  hi  the  following  table,  although  much  less  com- 
plete than  the  one  given  above,  will  serve  to  point  out  the  varia- 
tions in  quality  likely  to  be  found  in  unbleached  sulphite  fibre. 
They  are  all  of  pulp  made  from  spruce  wood. 

ANALYSES  OF  UNBLEACHED  SPRUCE  SULPHITE  FIBRE. 

(Quick  Cooking  Process.') 


Moisture,  loss  at  100°  C.      .    .     .     .    . 

Mineral  matter  (ash) 

Hydrocellulose,  etc.  (soluble  in  alkali)  . 

Cellulose. 

Non-cellulose  ("  lignin  ")  by  difference 


0.15 
1.00 
2.53 
86.32 
5.01 


6.70 
0.45 

2.20 

80.74 

0.85 


6.57 
0.33 
4.25 
88.12 
0.73 


6.45 

0.65 

1.52 

81.51 

9.87 


In  studying  these  analyses,  it  will  be  noticed  that  the  propor- 
tions of  cellulose  and  of  the  incrusting  matter  remaining  with  it 
greatly  in  the  different  samples.     This  is  a  point  of  much 


THE  SULPHITE  PROCESS. 


practical  importance,  especially  when  the  pulp  is  to  be  bleached, 

since  all  this  incrusting  matter  must  be  destroyed  by  the  bleaching 

powder.     Jf  the  incrusting 

matter  is  present   in   large 

amount,  the  consumption  of 

bleach    becomes    excessive, 

and  the   pulp   shows   great 

shrinkage. 

We  have  made  in  our 
laboratory  a  large  number 
of  determinations  showing 
the  yield  and  character  of 
pulp  obtained  by  the  sul- 
phite process  from  different 
wood.  In  these  experiments 
we  have  used  a  digester 
(Fig.  63)  built  of  bronze, 
lead-lined,  and  holding 
about  12  litres.  A  drop 
tube,  passing  from  the  top 
nearly  to  the  bottom  of 
the  digester,  was  utilized 
as  an  oil  bath  for  carry- 
ing the  thermometer,  while 
pressures  were  shown  upon 
an  ordinary  gauge. 

The   accompanying  table 
gives  the  results  of  these  experiments.     The  figures  give  the  per 
cent,  of  fibre  obtained  from  the  dry  wood. 

Spruce 50.75 

Poplar 55.18 

Cottonwood 50.80 

Gum 45.73 

Beech 42.80 

Birch .  53.80 

Maple 52.61 

Fungoid  Growth  on  Fibre.  —  The  black  specks  having  the 
appearance  of  mildew,  and  which  sometimes  appear  on  unbleached 
fibre  which  is  stored  for  a  considerable  length  of  time  when  in 


FIG.  63.  —  EXPERIMENTAL 


-270  Tim  CHEMISTRY  Of 


moist  condition*  have  been  carefully  studied  by  Herzberg,  whose 
examination  proves  them  to  be  due  to  a  fungoid  growth  upon 
the  fibre.  The  sample  of  pulp  examined  was  prepared  by  the 
Ilitter-Kellner  process,  and  was  disfigured  by  numerous  black 
spots,  varying  in  size  from  that  of  a  pin  head  to  that  of  a  pea. 

The  appearance  was  quite  different  from  that  occurring  in  straw 
cellulose  which  has  been  stored  in  damp  places.  Microscopical 
examinations  demonstrated  the  existence  of  a  fungoid  growth, 
twining  around  the  cellulose  fibres  as  ivy  does  around  a  tree.  The 
brown  color  of  its  mycelium  caused  the  patches  of  it  to  be  visible 
to  the  naked  eye  as  dark  specks.  It  was  thought  that  the  germs 
had  been  derived  from  the  river  water  used  in  the  manufacture, 
spring  water  not  being  available,  but  it  is  more  likely  that  they 
came  from  the  air,  finding  a  good  soil  on  the  moist  cellulose. 

Calcium  sulphite  was  recognized  on  the  spot*?  by  Frank's  method 
with  iodine  solution,  and  if  this  be  viewed  as  the  cause  of  the 
growth,  the  obvious  remedy  is  to  avoid  its  presence  in  the  finished 
product  ;  on  the  other  hand,  the  acid  juices  of  the  growth  itself 
will  tend  to  liberate  sulphurous  acid  from  the  calcium  sulphite, 
and  "arrest  its  development.  Thorough  drying  is  an  efficient  pre- 
ventative,  and  where  this  is  impracticable  the  use  of  a  very  weak 
solution  of  zinc  chloride  is  said  to  act  as  a  reliable  antiseptic  in 
killing  the  germs. 

It  w«os  observed  that  a  paper  made  from  pure  rags  and  highly 
sized  with  rosin  developed  a  fungoid  growth  when  kept  in  a  warm, 
damp  place.  There  is  no  direct  evidence  to  show  whether  the 
germs  are  derived  from  the  water  or  air.  Adequate  nutriment  for 
the  mould  is  supplied  by  size  of  animal  origin,  and  even  when 
rosin  i's  used  the  accompanying  starch  may  prove  sufficient. 

The  Waste  Liquor.  —  The  waste  liquors  from  a  well-conducted 
sulphite  boiling  are  of  a  light  golden-brown  color,  and  contain,  in 
solution,  or  in  combination  with  the  bisulphite,  about  50  per  cent. 
of  the  weight  of  the  dry  wood.  If  lime  is  added  to  such  liquors, 
a  considerable  portion  of  this  organic  matter  is  thrown  down,  and 
mpnosulphite  of  lime  produced.  The  addition  of  a  soluble  alkali 
like  soda  determines  the  precipitation  of  the  organic  matter  in 
brown  flocks.  On  account  of  the  action  of  the  sulphurous  acid 
in  preventing  oxidation,  the  organic  matter  in  the  solution  has 
not  undergone  great  chemical  change,  but  exists  in  somewhat  the 
same  condition,  as  far  as  its  chemical  relations  are  concerned,  as 


THE  SULPHITE  PROCESS.  271 

in  the  incrusting  matter  of  the  wood,  and  it  is  probable  that,- with 
the  further  development  of  the  sulphite  process,  methods  will  be 
worked  out  by  which  this  large  amount  of  waste  material  may 
be  utilized.  The  most  obvious  direction  for  such  methods  to  take 
will  be  toward  the  preparation  of  glucose,  alcohol,  and  oxalic  and 
pyroligneous  acids,  since  well-known  processes  are  now  in  opera- 
tion for  making  these  compounds  from  similar  materials. 

The  waste  sulphite  liquors  have  been  found  to  contain,  besides 
calcium  sulphite  and  sulphate,  mannose,  galactose,  and  vanillin, 
and  to  yield,  upon  distillation  with  sulphuric  or  hydrochloric  acid, 
furfurol  or  furfuramide,  proving  that  pentaglucoses  are  present. 
Of  these  xylose  1  has  been  found. 

According  to  Cross  and  Be  van,  the  double  compounds  of  the 
aldehydes  and  bisulphites  in  the  waste  liquor  are  not  broken  up 
by  dialysis,  and  are  precipitated  unchanged  by  alcohol,  or  alcohol 
and  ether. 

Mitscherlich  has  shown  that  there  exists  in  the  solution  a  com- 
pound apparently  similar  to  tannin,  at  least  so  far  as  its  power 
to  precipitate  glue  goes,  and  he  has  based  upon  this  fact  a  method 
involving  the  use  of  spent  sulphite  liquors  in  sizing  paper.  In 
Germany  the  farmers  in  the  neighborhood  of  -the  sulphite  mills 
find  that  the  waste  liquors  are  of  considerable  value  in  preventing 
the  escape  of  ammonia  when  sprinkled  upon  compost  heaps. 

Dr.  W.  Bucldeus,  in  the  Papier-Zeitung  of  March  19,  1891,  has 
an  interesting  summary  of  the  results  obtained  by  an  investigation 
of  the  composition  of  the  waste  liquor  and  the  substances  derived 
therefrom.  We  give  his  results  somewhat  in  detail:  — 

The  waste  liquor  was  neutralized  with  ammonia,  the  lime  was 
precipitated  by  ammonium  carbonate,  and  the  carbonate  of  lime 
thus  formed  was  separated  by  filtration.  The  dark  brown  filtrate 
was  evaporated,  and  the  dried  residue  distilled.  The  residue  con- 
tained 7.2  per  cent,  ammonia  as  salts.  Water  and  a  yellow-colored 
oil  were  obtained  in  the  condenser,  and  finally  a  crystalline  subli- 
mate appeared  on  the  walls  of  the  tube.  The  gases  escaping  were 
caught  in  the  gasometer.  The  oil,  at  first,  had  an  odor  like  mer- 
captan,  but  this  disappeared  on  heating  slightly.  This  odor  was, 
without  doubt,  due  to  organic  sulphur  compounds  which  were 
present  ih  traces.  The  oil  and  water  were,  after  this  heating, 

1  Xylose,  the  sugar  of  wood,  jnelts  at  144°  C.,  and  is  dextro-rotary.  Upon  boiling 
with  dilute  sulphuric  acid,- it  yields  wood  gum. 


27 2  THE  CHEMISTRY  OF  PAPER-MAKING. 

distilled  with  steam.  The  distillate  was  shaken  out  with  ether, 
then  dried,  and  the  ether  evaporated  over  calcium  chloride.  A 
brown  oil  remained,  which  boiled  at  130°  C.,  and  which  colored 
a  fine  chip,  moistened  with  hydrochloric  acid,  a  strong  carmine, 
and  which  was  therefore  believed  to  be  pyrrol.  Pyrocatechin  was 
also  obtained  in  the  distillate,  as  was  proved  by  color-tests  wiiJi 
iron  salts,  and  its  reduction  of  Fehling's  solution. 

The  gases  were  carbon  moxide,  hydrogen,  marsh  gas,  and  sul- 
phureted  hydrogen.  400  grammes  of  the  residue  yielded  180 
grammes  of  coke,  30  litres  of  gasr  and  200  grammes  of  distillate. 

Mucic  and  saccharic  acid  could  not  have  been  present  as  such 
in  the  liquor,  because  they  are  formed  by  the  oxidation  of  carbo- 
hydrates, and  the  action  of  the  liquor  is  a  reducing  one.  Pyrrol 
is  formed  by  the  distillation  of  ammonium  salts  of  these  two  acids. 
The  only  way  of  accounting  for  pyrrol  is  the  presence  of  succinic 
acid,  which  is  very  probably  present  owing  to  the  occurrence  of 
resins  in  the  wood.  Ammonium  succinate  changes  readily  by 
splitting  off  of  water  into  ammonia  succinamide,  which  by  heating 
with  reducing  agents  gives  pyrrol. 

The  presence  of  pyrocatechin  is  due  to  that  of  dioxybenzoic  acid 
(1,  3,  4),  which  is  in  the  liquor  as  dipyrocatechuic  acid.  The 
decomposition  of  this  by  distillation  with  ammonia  is  a  source 
of  tannic  acid  and  pyrocatechin.  There  is,  according  to  Dr. 
Buddeus,  no  tannic  acid  present  in  the  liquor,  which  will  give 
a  blue-black  color  with  ferric  chloride,  because  the  tannin  in  wood 
is  reduced  by  cooking  with  sulphurous  acid.  The  reduction  is 
probably  to  dipyrocatechuic  acid,  but  by  treating  with  ammonia 
and  distilling,  tannic  acid  is  eventually  formed.  Sulphites  are 
oxidized  to  sulphates  when  the  tannin  is  reduced.  It  may  be, 
therefore*  that  the  difficulty  of  pulping  wood  rich  in  tannin  by 
the  sulphite  process  is  due  to  the  action  of  the  tannin,  which 
renders  the  sulphurous  acid  ineffective. 

According  to  Schubert,  the  greatest  difficulty  with  which  Ger- 
man manufacturers  of  sulphite  pulp  have  to  contend,  is  found 
in  the  disposal  of  the  waste  liquor  and  wash  waters*  The  laws 
there  are  far  more  stringent  than  in  this  country  in  respect  to  the 
pollution  of  streams,  and  the  number  of  water-courses  of  consider- 
able size  is  also  comparatively  small.  No  practical  method  is 
known  for  eliminating  the  sulphurous  acid  and  organic  matter 
in  the  waste  liquor. 


THE  SULPHITE  PROCESS.  273 


The  evaporation  of  the  liquor  offers  no  solution  of  the  difficulty, 
and  the  product  is  of  absolutely  no  value  as  fuel.  The  waste 
liquors  are  in  Germany  often  run  off  in  open  liquor  ponds,  where 
they  are  allowed  to  soak  in  the  ground.  These  ponds  in  time 
develop  a  very  unpleasant  odor  and  seriously  contaminate  the 
wells  of  the  neighborhood.  The  impure  wash  waters,  when 
allowed  to  run  in  small  streams,  set  up  conditions  which  seem 
peculiarly  adapted  to  the  growth  of  algse. 

According  to  the  experiments  of  Dr.  Weigelt-Reufach,  liquors 
containing  from  0.6  to  0.75  per  cent  of  sulphurous  acid  require 
dilution  with  fifteen  hundred  times  their  volume  of  water  in  order 
to  render  them  harmless  to  fish  and  other  forms  of  animal  life. 
The  action  of  the  sulphurous  acid  is,  of  course,  to  lower  in  the 
water  the  proportion  of  dissolved  oxygen  which  the  fish  cannot 
breathe.  The  precipitated  resins  and  gummy  matters  are  them- 
selves injurious,  not  so  much  on  account  of  any  poisonous  quality, 
as  of  their  action  in  coating  over  the  gills  and  shutting  off  the 
supply  of  oxygen,  as  pointed  out  by  Dr.  Frank. 

It  is  of  course  evident  that  nearly  as  much  material  from  the 
wood  is  carried  away  in  the  waste  liquors  as  is  obtained  as  pulp, 
and  the  quantity  of  organic  matter  thus  discharged  by  a  large  mill 
is  therefore  very  great.  The  waste  liquor  from  a  Mitscherlich 
boiling  contained  per  litre,  — 

Sulphurous  acid 3.86  grammes, 

Sulphuric  acid 7.33       " 

Chlorine 0.29       " 

and  by  evaporation  of  one  litre,  and  drying  at  110°  C.,  yielded 
109  grammes  of  residue,  which  on  ignition  left  19  grammes  of  ash 
containing,  — 

Sesquioxide  of  iron 0.02  grammes. 

Lime 10.30        « 

Magnesia 0.30        " 

Potash 0.28       " 

Soda 0.10       « 

11.00  grammes. 

There  were,  therefore,  in  the  liquor  90  grammes  of  organic 
matter  per  litre,  or  90  kilogrammes  per  cubic  metre,  or  5400  kilo- 
grammes per  charge  of  60  cubic  metres. 

Traces  of  sulphurous  acid  gas  are  almost  constantly  present  in 


274  THE  CHEMISTRY  OF  PAPER-MAKING. 


the  atmosphere  within  or  immediately  around  a  sulphite  mill,  and 
where  apparatus  or  methods  are  defective  the  proportion  of  gas 
is  likely  to  be  so  great  as  to  become  a  source  of  much  annoyance. 
Even  small  quantities  of  the  gas  produce,  when  inhaled,  consider- 
able irritation  of  the  mucous  membrane  of  the  throat  and  lungs. 
In  consequence  of  this  irritation  the  tendency  to  take  cold  is 
increased,  and  if  the  irritation  persists,  a  chronic  cough  or  bronchi- 
tis may  be  established.  The  effects  of  the  gas  upon  plants  and 
animals  have  been  carefully  studied  by  numerous  observers,  whose 
conclusions  are  by  no  means  in  harmony  with  each  other.  There 
seems  to  be  no  doubt,  however,  that  even  small  proportions  of  the 
gas  are  injurious  to  both  animals  and  plants,  but  we  are  inclined 
to  think  that  much  of  the  ill  effect  which  has  been  charged  to  the 
gas  alone  has  been  caused  by  the  practice,  which  was  at  one  time 
common,  of  blowing  the  digesters  off  into  the  open  air,  so  that  all 
the  neighboring  vegetation  was  covered  with  a  film  of  condensed 
liquor  in  which  free  sulphuric  acid  was  afterwards  developed  by  oxi- 
dation. This  practice  is  now  happily  done  away  with  everywhere. 

According  to  Schroeder  both  deciduous  a'nd  evergreen  trees 
absorb  sulphurous  acid  through  their  leaves  from  air  containing 
as  little  as  one  five-thousandth  of  the  gas  by  volume.  The  leaves 
retain  it  mostly,  but  a  small  portion  penetrates  into  the  leaf  stalks 
and  bark,  where  it  may  be  found  either  as  sulphurous  or  sulphuric 
acid.  Evergreen  trees  are  less  sensitive  in  this  respect  »than  others. 

Stockhart  finds  that  a  distance  of  630  metres  is  sufficient  to 
protect  all  vegetation  if  the  vapors,  even  in  large  quantity,  escape 
from  a  chimney  82  feet  high. 

Dr.  Ogata  has  made  a  series  of  experiments  on  animals  in  Pet- 
tenkof er's  laboratory.  He  finds  that  different  animals  differ  greatly 
in  their  susceptibility  to  the  action  of  the  ga  j  frogs  being  most 
sensitive,  then  mice,  rabbits,  and  guinea  pigs,  in  the  order  named. 
As  little  as  0.04  per  cent,  affected  all  the  animals  mentioned.  A 
mouse  died  after  two  hours'  exposure  to  an  atmosphere  containing 
only  0.06  per  cent. ;  a  guinea  pig  after  seven  hours'  exposure  to  an 
atmosphere  containing  0.24  per  cent.  The  poisonous  effect  seems 
to  be  due  to  the  action  of  the  sulphurous  acid  on  the  blood,  which 
absorbs  the  gas  and  oxidizes  it  to  sulphuric  acid. 

Hurt  claims,  however,  that  air  containing  even  as  much  as  4  per 
cent,  of  the  gas  has  no  permanent  ill  effect  on  the  health  of  human 
beings,  but  one-tenth  of  that  amount  occasions  difficulty  of  breath- 
ing (Wagner). 


BLEACHING.  275 


CHAPTER  IV. 

BLEACHING. 

NONE  of  the  commercial  processes  for  separating  cellulose  which 
have  been  thus  far  considered  yield  this  material  in  a  state  of  com- 
plete purity.  It  is  always  associated  with  a  portion  of  the  lignin 
or  incrusting  matter  originally  present  in  the  raw  fibre,  and  various 
coloring-matters  may  also  be  present.  The  lignin  is  more  or  less 
modified  by  the  treatment  to  which  the  fibre  has  beenxsubjected,  and 
the  coloring-ma tters  may  be  either  those  which  have  survived  this 
treatment,  or  those  which  have  been  developed  as  a  consequence 
of  it.  The  coloring-matter  properly  so-called  usually  forms  only 
a  small  proportion  of  the  foreign  material,  so  that  most  of  the 
work  of  the  bleaching  agent  is  spent  in  the  destruction  of  lignin 
and  those  derivatives  of  lignin  which  were  formed  and  left  upon 
the  fibre  in  the  processes  of  reduction.  The  process  of  bleaching, 
by  which  these  impurities  which  cover  up  the  natural  white  of  the 
pure  cellulose  are  removed,  is  essentially  a  process  of  oxidation, 
and  depends  for  its  success  upon  the  fact  that  the  substances  asso- 
ciated with  the  cellulose  are  more  easily  oxidized  and  split  up  into 
soluble  products  by  an  oxidizing  agent  than  the  comparatively 
stable  cellulose  which  forms  the  basis  of  the  impure  fibre.  The 
destruction  of  these  impurities  may  be  brought  about  through  the 
action  of  almost  any  of  the  well-known  oxidizing  agents,  and  many 
of  them  have  been  applied  for  this  purpose  with  more  or  less  suc- 
cess. Practically,  however,  all  bleaching  is  effected  by  the  use 
of  chlorine,  or  compounds  of  chlorine,  which,  in  the  presence,  of 
moisture,  set  up  reactions  by  which  oxygen  is  liberated.  Of  these 
compounds  the  hypochlorite  of  calcium,  "chloride  of  lime,"  or 
ordinary  bleaching-powder,  is  by  far  the  most  important. 

The  commonly  accepted  and  probably  the  true  theory  of  hypo- 
chlorite bleaching  is,  therefore,  that  the  destruction  of  the  coloring- 
matter  is  due  primarily,  not  to  the  action  of  the  chlorine,  but  to 
that  of  oxygen  which  is  set  free  in  the  decomposition  of  water 
brought  about  by  the  chlorine,  which  unites  with  the  hydrogen  of 


276  THE  CHEMISTRY  OF  PAPER-MAKING. 

the  water  to  form  hydrochloric  acid.  Bleaching,  therefore,  becomes 
a  form  of  burning  or  wet  combustion,  in  which  the  coloring-matters 
are  oxidized  by  the  liberated  oxygen,  the  final  products  of  the 
oxidation  being  carbonic  acid  and  water ;  while  the  cellulose,  being 
freed  from  the  foreign  matter  with  which  it  was  at  first  associated, 
appears  in  its  natural,  uncolored  condition.  Dry  chlorine  has  no 
bleaching  action  whatever,  as  may  be  shown  by  placing  a  piece  of 
litmus  paper,  or  a  piece  of  cloth  dyed  a  delicate  tint,  in  a  jar  filled 
with  the  dry  gas.  If  care  has  been  taken  to  exclude  all  moisture, 
there  will  be  no  change  in  the  color  after  several  hours'  exposure 
to  the  gas ;  but  upon  the  addition  of  water  the  color  is  instantly 
discharged.  Chlorine  does  not,  as  a  rule,  destroy  mineral  colors, 
or  the  blacks  and  grays  produced  by  lampblack  or  deposited 
carbon. 

Chlorine  was  first  applied  to  bleaching  by  Berthollet  in  1785, 
who  employed  a  solution  of  the  gas  in  water.  Tennant  in  1798 
patented  a  liquid  bleach,  which  was  a  solution  of  calcium  or  sodium 
hypochlorite,  prepared  by  passing  the  gas  into  milk  of  lime  or  a 
solution  of  caustic  soda.  This  bleaching  agent  was  necessarily 
difficult  to  transport  and  keep,  and  in  1799  he  introduced  a 
great  improvement  by  preparing  a  solid  bleaching  agent  by  pass- 
ing the  chlorine  gas  over  slaked  lime,  which  absorbed  it  with 
formation  of  hypochlorite  of  calcium. 

Despite  the  obvious  advantages  offered  by  the  use  of  bleaching- 
powder,  its  introduction  was  very  slow,  and  there  are  doubtless 
many  paper-makers  in  this  country  whose  recollections  go  back 
to  the  time  of  gas  bleaching.  In  working  this  method  chlorine 
gas  was  generated  at  the  mill  by  the  action  of  sulphuric  acid  upon 
a  mixture  of  peroxide  of  manganese  and  common  salt  in  a  stone  or 
stoneware  retort  fitted  with  earthenware  pipes,  through  which  the 
gas  was  conducted  to  the  moist  pulp  stored  in  the  drainer.  The 
inconvenience  and  disadvantages  of  this  early  method  were  so 
great  that  it  has  now  been  wholly  discarded  in  favor  of  the  more 
manageable  bleaching-powder. 

The  method  of  preparation  of  ordinary  bleaching-powder  has 
been  described  in  Part  I.,  and  the  various  methods  for  testing  its 
value  will  be  found  in  the  chapter  on  Chemical  Analysis.  As 
ordinarily  manufactured  it  is  white  powder  having  a  somewhat 
pungent  but  not  disagreeable  odor  of  chlorine.  If  very  strong,  it 
usually  contains  some  lumps.  When  exposed  to  the  air  it  rapidly 


BLEACHING.  277 


absorbs  moisture,  and  is  converted  into  a  sticky  mass,  or  even  into 
a  gray  mud.  The  exact  chemical  composition  of  .bleaching-powder 
has  been  a  matter  of  some  controversy,  but  the  formula  CaOCl2 
proposed  by  Lunge  is  now  being  generally  accepted.  The  com- 
mercial value  of  the  material  depends  upon  the  amount  of  chlo- 
rine present  as  hypochlorite,  this  chlorine  being  commonly  called 
"  available  chlorine/'  In  the  freshly  manufactured  article  the  per- 
oeritage  of  available  chlorine  may  be  as  high  as  41 ;  but  as  found 
in  our  markets,  and  owing  to  the  deterioration  which  always  takes 
place  in  storage,  the  percentage  of  available  chlorine  is  rarely 
above  37,  and  anything  over  36  is  usually  accepted  as  satisfactory. 
The  strength  of  bleaching-powder  is  estimated  in  France  in 
degrees,  which  represent  the  number  of  litres  of  chlorine  gas  at 
0°  0.  and  760  mm.  pressure  which  can  be  liberated  from  one  kilo 
of  the  sample.  The  relation  which  these  degrees  bear  to  the  per- 
centage of  effective  chlorine  is  shown  below :  — 

French          Per  cent,  effective  French  Per  cent,  effective 

degrees.  chlorine.  degrees.  chlorine. 

65  20.65  100  31.80 

70  22.24  105  33.36 

75  23;83  110  34.95 

80  25.42  115  36.54 

85  27.01  120  38.13 

90  28.60  125  39.72 

95  30.21  130  41.34 

One  litre  of  chlorine  weighs  3.18  grammes,  and  the  percentage 
may  therefore  be  calculated  by  multiplying  the  French  degrees  by 
0.318. 

The  deterioration  of  the  strength  of  bleaching-powder  is  very 
rapid  when  the  powder  has  been  wet,  as  sometimes  occurs  on  ship- 
board, and  we  have  tested  samples  containing  less  than  28  per  cent, 
of  available  chlorine.  In  rare  cases  the  powder  is  liable  to  sudden 
decomposition,  in  which  oxygen  is  liberated,  and  instances  are  on 
record  in  which  casks  of  bleach  have  exploded  from  this  cause. 

The  best  series  of  experiments  which  have  come  under  our 
notice  having  for  their  object  the  determination  of  the  rate  at 
which  bleaching-powder  deteriorates  in  storage  are  those  of  Pat- 
tinson,  which  extended  over  a  year,  arid  were  concluded  in  1886, 
He  took  3  casks  of  the  usual  size,  each  containing  about  6  cwt.  of 
bleaching-powder;  12  bottles  of  each  kind  of  powder  were  filled  at 


278 


THE  CHEMISTRY  OF  PAPER-MAKING. 


the  same  time,  the  casks  sealed,  and  both  casks  and  bottles  stored 
in  a  cellar.  A  maximum  and  minimum  thermometer  was  placed 
near  them,  and  a  careful  record  of  the  temperature  made  for  each 
working  day  of  the  year.  The  record  shows  the  temperature  to 
have  been  uniform  and  comparatively  low  during  the  entire  year, 
the  highest  being  62°  F.,  and  the  lowest  38°  F.  One  bottle  from 
each  of  the  3  sets  of  12  was  opened  and  tested  each  month,  and  a 
sample  was  also  withdrawn  and  tested  from  each  of  the  3  casks. 
The  results  of  the  experiments  show  a  gradual  and  regular  loss 
of  available  chlorine  during  the  time  over  which  the  tests  were 
made.  The  average  loss  in  the  cask  samples  was  about  a  third  of 
1  per  cent,  greater  than  in  the  bottle  samples,  as  the  casks  were 
necessarily  not  air-tight.  A  complete  analysis  of  each  of  the  cask 
samples  was  made  at  the  beginning  and  also  at  the  end  of  the 
experiment.  These  analyses  are  given  in  the  table  below :  — 

COMPOSITION  OF  BLEACHING-POWDER. 


January  29,  1885. 

January  5,  1886. 

ABC 
87.00      38.30      36.00 

ABC 
33  80      35.10      32.90 

Chlorine  as  chloride    .... 
Chlorine  as  chlorate    .... 

0.35        0.59        0.32 
0.25        0.08        0.26 
44.49      43.34      44.66 

2.44        2.42        1.97 
0.00        0.00        0.00 
43.57      42.64      48.65 

0.40        0.34        0.43 

0.31        0.36        0.38 

Silicious  matter  
Carbonic  acid     ...... 
Alumina,  peroxide  iron,  oxide  i 
manganese                              / 

0.40        0.30        0.50 
.0.18        0.30        0.48 

0.48        0.45        0.85 
16.45      16.33      17.00 

0.50        0.40        0.50 
0.80        1.48        1.34 

0.40        0.40        0.37 
18.18      17.20      18.89 

100.00    100.00    100.00 

100.00    100.00    100.00 

Total  chlorine      

37.60      38.97      36  58 

36.24      37.62      34.87 

The  small  quantity  of  chlorine  found  as  chlorate  at  the  begin- 
ning of  the  experiments  ceased  to  exist  in  this  combination  at  the 
end,  and  from  tests  made  it  was  found  that  all  the  chlorate  had 
disappeared  in  May,  or  about  four  months  after  the  casks  were 
filled.  The  amount  of  chlorine  existing  as  chloride  had  slightly 
increased.  It  is  not  often  the  bleaching-powder  can  be  stored  where 
so  low  a  temperature  as  60°  F.  can  be  maintained  for  any  length 
of  time,  especially  in  the  summer  months,  when,  as  previous  experi- 
ments have  indicated,  the  greatest  loss  of  available  chlorine  takes 
place. 


BLEACHING.  279 


Bleaching-powder  should  be  stored  in  as  dry  a  place  ar  possible, 
or,  better,  in  one  that  is  both  dry  and  cool ;  and  if  any  casks  are 
damaged,  they  should  be  the  first  ones  selected  for  use,  as  deterio- 
ration is  likely  to  proceed  more  rapidly  in  them  than  in  sound  casks. 

The  rate  at  which  the  powder  deteriorates  is  largely  influenced 
by  the  Duality  of  the  cask  in  which  it  is  packed.  The  soft  woods 
are  considerably  affected  by  the  action  of  the  powder,  and  shrink 
badly  when  exposed  to  the  sun.  In  any  subsequent  exposure  to 
rain,  therefore,  the  water  readily  finds  its  way  into  the  cask.  Ash 
and  other  hard  woods  may  be  properly  used  for  staves ;  but  the 
best  casks  are  built  of  oak  staves  one  inch  in  thickness.  The  pores 
of  oak  are  very  close,  and  almost  impervious  to  the  air,  and  if,  as  was 
formerly  the  usual  case,  the  staves  had  previously  been  used  for  raw 
sugar  or  molasses  casks,  they  are  still  better  fitted  to  preserve  the 
bleach.  Many  makes  of  bleach  arrive  in  casks  with  staves  ^-inch 
or  f -inch  in  thickness,  but  thicker  staves  are  to  be  recommended. 

For  the  preparation  of  the  hypochlorite  solution,  one-half  the 
contents  of  the  cask  are  dumped  into  about  1000  gallons  of  water  in 
an  agitator  tank  which  is  built  of  iron  and  well  painted  wiith  red  lead. 
Agitation  of  the  mixture  is  continued  until  all  lumps  are  broken 
up.  The  agitator  Is  then  stopped,  and  the  greater  portion  of  the  mud 
allowed  to  settle,  after  which  the  cloudy  liquid  standing  above  is 
drawn  out  into  shallow  tanks  to  complete  the  deposition  of  sedi- 
ment. The  mud  remaining  in  the  agitator  is  again  treated  with 
a  fresh  quantity  of  water,  and  the  weak  liquor  thus  obtained  is 
drawn  off  into  another  tank,  and  used  in  the  first  treatment  of  the 
next  lot  of  bleaching-powder.  The  mud  should  be  tested  from 
time  to  time  for  available  chlorine,  as  unless  the  washing  is  thor- 
oughly performed  a  considerable  loss  may  occur. 

We  are  indebted  to  Hoffmann's  Handbook  for  the  following 
analysis  of  the  mud  from  chloride  of  lime  solutions.  On  account 
of  the  variation  in  the  quality  of  bleaching-powder,  however,  this 
analysis  cannot  do  more  than  indicate  in  a  general  way  the  char- 
acter of  the  mud. 

ANALYSIS  OF  DRY  MUD  FROM  BLEACHING-POWDER  SOLUTION. 

Hydrate  of  lime  (CaHjOs)     •     •    • 59.28 

Carbonate  of  lime 27.81 

Chlorite  of  calcium 5.98 

Oxide  of  iron  and  alumina 1.00 

Water  5.42 


280  THE  CHEMISTRY  OF  PAPER-MAKING. 

Only  the  clear  solution  prepared  as  above  should  be  used  for 
bleaching,  not  only  because  it  acts  more  quickly  than  a  cloudy  one 
which  contains  considerable  free  lime,  but  also  in  order  to  avoid  dirt. 
Many  of  the  black  specks  noticed  in  paper  are  due  to  dirt  in  the 
bleach.  When  from  this  source,  they  generally  consist  of  iron 
oxide,  and  traces  of  copper  may  be  found  in  them.  The  best 
strength  of  liquor  for  storage  and  for  economy,  and  thorough 
washing  of  the  mud,  is  about  5°  Be*.  The  hydrometer  gives,  of 
course,  only  a  rough  approximation  to  the  strength  of  the  bleach, 
since  both  the  chlorate  and  chloride  of  calcium  affect  the  instru- 
ment quite  as  much  as  the  hypochlorite,  but  as  a  rough  rule  it 
may  be  stated  that  1°  Be*,  averages  about  0.47  per  cent,  available 
chlorine  in  the  solution. 

The  bleaching  of  paper-stock  is  performed  either  in  chests  or 
engines.  Rags  and  jute  are  bleached  in  engines,  wood  and  simi- 
lar fibres  more  commonly  in  chests.  The  difficulty  of  securing 
thorough  agitation  and  evenness  of  color  in  chests  is  an  objection, 
and  their  use  requires  a  larger  plant  to  do  the  same  amount  of 
work. 

The  amount  of  bleaching-powder  actually  consumed  in  bringing 
stock  to  color  depends  mainly,  of  course,  upon  the  thoroughness 
with  which  the  non-cellulose  has  been  removed  by  the  previous 
treatment.  On  this  account  the  results  obtained  by  different  mills 
in  bleaching  the  same  fibre  show  considerable  variation.  It  is  to 
be  noted,  moreover,  that  the  mills  base  their  figures  upon  the 
weight  of  bleach  in  the  cask,  and  that  considerable  losses  may 
occur  in  mixing  the  bleach  and  washing  the  mud.  The  follow- 
ing may  be  taken  as  the  usual  quantities  of  bleaching-powder 
required  per  100  Ibs.  of  the  different  fibres. 

Lbs. 

Rags  .     .    '•,'  .    'f.   ,.:  ~.     .    .'".;'.'.  .V.  .    2-5 

Straw 7-10 

Esparto 10-15 

Soda  Poplar    ...........  12-15 

Soda  Spruce 18-25 

Sulphite  Poplar  . .  14-20 

Sulphite  Spruce 15-25 

Jute 10-20 

The  full  proportion  of  bleach  in  the  form  of  a  5°  Be*,  solution 
is  usually  added  after  the  stock  has  been  well  beaten  up.  It  is 


BLEACHING,  281 


best  to  have  the  stuff  as  thick  as  possible  without  interfering  with 
thorough  agitation.  The  general  tendency  is  to  add  considerably 
more  bleach  than  the  stock  requires.  This  has  the  effect  of 
hastening  the  operation,  but  the  loss  in  the  drainage  water  may 
be  great. 

We  have  frequently  tested  the  liquor  in  the  chest,  in  order  to 
determine  the  proportion  of  chlorine  present  after  the  pulp  had 
come  to  color,  and  have  found  in  many  cases  that  it  amounted  to 
onp-quarter  or  more  of  that  originally  introduced. 

The  bleaching  of  rags  is  a  comparatively  easy  operation,  since 
the  preliminary  treatment  has  removed  nearly  all  the  material 
other  than  cellulose.  The  half-stuff  is  always  bleached  in  the 
engine,  and  requires  from  2  to  5  per  cent,  of  bleaching-powder. 
A  small  amount  of  acid  is  often  added  when  color  is  nearly 
reached,  and  in  the  best  practice  the  stock  is  dumped  into  drainers, 
and  there  gradually  brought  to  full  color  by  the  last  portions  of 
bleach  remaining  in  the  stock. 

Wood  fibre  is  bleached  either  in  engines  or  chests,  the  latter 
practice  being  more  common.  The  pulp  is  sometimes  dumped 
into  the  drainer  after  a  treatment  of  about  two  hours  in  the  engine 
with  strong  bleach  solution.  Bleaching  in  the  chest  requires  from 
six  to  sixteen  hours,  according  to  the  character  of  the  pulp,  and, 
on  account  of  the  difficulty  of  securing  thorough  agitation,  is  less 
likely  to  give  an  even  color,  especially  when  the  stock  during 
bleaching  is  heated  by  steam. 

After  the  pulp  has  come  to  color  the  action  of  the  bleach  should 
be  arrested  as  soon  as  possible,  either  by  washing  or  the  use  of 
an  antichlor,  as  otherwise  the  cellulose  itself  is  likely  to  have  its 
strength  and  quality  impaired  through  the  continued  oxidizing 
action  of  the  hydrochlorite. 

The  operation  of  bleaching  is  frequently  accelerated  by  heating 
the  mixture  of  pulp  and  bleach  liquor  by  means  of  a  steam  pipe 
passing  to  the  bottom  of  the  chest  or  engine.  Considerable  care 
is  necessary  in  order  to  avoid  over-heating ;  and  if  the  temperature 
much  exceeds  100°  F.  the  chlorine  is  likely  to  attack  the  cellulose, 
forming  organic  chlorides,  which  remain  with  the  fibre  and  cause 
the  color  to  go  back.  This  chiorination  of  the  fibre  is  likely  to 
occur  when  a  considerable  proportion  of  lignin  is  present,  and  it 
is  claimed  that  where,  as  in  the  case  of  soda  poplar  pulp,  the 
lignin  has  been  entirely  removed,  a  considerably  higher  tempera- 


282  THE  CHEMISTRY  OF  PAPER-MAKING. 

ture  may  be  maintained  without  injury  to  the  stock.  Although 
there  is -an  undoubted  saving  of  time  by  hot  bleaching,  the  experi- 
ments of  Cross  and  Be  van  indicate  that  the  consumption  of  bleach 
is  increased  about  20  per  cent.,  in  order  to  secure  the  same  result 
as  regards  color. 

The  admission  of  steam  into  the  bottom  of  a  deep  chest  intro- 
duces a  danger  which  it  is  difficult  to  avoid.  If  the  movement  of 
the  pulp  is  slow,  or  if  the  stuff  is  very  thick,  the  mixture  in  the 
lower  portion  of  the  chest  may,  on  account  of  the  imperfect  cir- 
culation, easily  become  so  hot  as  to  injure  the  pulp,  while  the  tem- 
perature at  the  surface  may  be  much  below  this  point.  Such 
local  over-heating  is  a  common  cause  of  uneven  color  in  the  fibre 
bleached  in  chests. 

In  order  to  free  the  cellulose  from  traces  of  chemicals  which 
are  likely  to  affect  its  permanence,  all  pulp  should  be  washed  after 
bleaching,  even  though  the  active  chlorine  has  been  "  killed "  by 
the  use  of  an  antichlor.  Small  traces  of  free  acid  or  of  chlorides 
cause  paper  to  deteriorate  rapidly  through  the  formation  of  hydro- 
cellulose  in  the  first  instance,  and  on  account  of  changes  set  up 
by  reactions  which  are  less  perfectly  understood  in  the  second. 
Chloride  of  alumina,  even  in  small  amounts,  is  known  to  have  a 
very  destructive  effect  upon  cellulose,  and  would  be  formed  on 
the  addition  of  alum  to  pulp  containing  chloride.  Traces  of  bleach 
seriously  impair  the  strength  of  pulp  by  converting  it  into  the 
brittle  oxycellulose.  This  action  is  well  shown  if  a  piece  of  cotton 
is  dipped  into  a  dilute  solution  of  bleach,  and  then  squeezed  nearly 
dry  and  exposed  to  the  air,  when  it  will  be  found  to  undergo  a 
gradual  disintegration. 

The  presence  of  traces  of  bleach  in  the  stock  may  be  readily 
detected  by  the  use  of  iodide  of  starch  paper  or  solution.  The 
latter  is  made  by  boiling  up  as  much  starch  as  would  go  on  a 
ten-cent  piece  with  five  or  six  ounces  of  water,  and  adding  a  few 
crystals  of  iodide  of  potash.  The  paper  is  prepared  by  dipping 
pieces  of  filter  paper  into  the  mixture.  The  paper  is  somewhat 
more  sensitive  if  used  at  once,  but  it  may  be  dried  and  preserved 
for  future  use.  If  a  drop  of  liquor  containing  bleach  is  brought 
in  contact  with  either  the  solution  or  the  paper,  iodine  is  liberated, 
and  forms  immediately  with  the  starch  a  deep  blue  compound. 
Two  precautions  should  be  observed  in  making  this  test;  if  the 
bleach  liquor  is  very  strong,  there  may  be  sufficient  chlorine  pres- 


BLEACHING.  288 


ent  to  destroy  the  blue,  while,  on  the  other  hand,  the  chlorine 
may  sometimes  be  so  nearly  exhausted  that  no  test  for  it  can  be 
obtained  from  the  liquor,  although  the  blue  color  appears  when  a 
drop  of  the  starch  reagent  is  allowed  to  fall  upon  the  pulp  itself 
from  which  the  liquor  has  previously  been  squeezed. 

A  yellowish  discoloration  is  sometimes  noticed  on  the  top  and 
edges  of  wet  bleached  pulp  which  has  been  kept  for  some  time. 
This  is  due  generally,  if  not  always,  to  imperfect  washing,  by 
which  all  the  calcium  chloride  is  not  removed  after  bleaching. 
The  evaporation  going  on  at  the  exposed  portions,  aided  by  the 
capillary  action  of  the  pulp  which  continually  brings  more  water 
from  the  interior  of  the  mass,  gradually  concentrates  the  solution 
of  chloride  which  may  at  first  be  extremely  dilute,  until  it  is 
strong  enough  to  act  upon  the  fibre  and  form  these  colored 
decomposition  products.  The  water  extract  from  such  yellow 
portions  is  found  by  us  to  be  dark  colored  and  bitter.  It  contains 
calcium  chloride  in  considerable  amount.  The  residue  left  after 
evaporating  the  extract  yields,  on  treatment  with  alcohol,  a  light 
brown  solution  which  gives  a  copious  yellow  precipitate  with  a 
neutral  alcoholic  solution  of  lead  acetate ;  the  substances  present 
in  the  extract  seem  to  be  nearly  allied  to  caramelane. 

The  time  required  and  difficulty  experienced  in  removing  the 
last  traces  of  bleach  from  the  pulp  by  washing  has  led  to  the  use 
of  various  chemicals  for  the  purpose  of  neutralizing  any  ^hypo- 
chlorite  left  in  the  stock.  Such  chemicals  are  called,  from  their 
office  in  this  connection,  Antichlors. 

Sodium  thiosulphate,  Na2S2O3,  5 H2O,  commonly  called  "hypo- 
sulphite of  soda,"  is  the  antichlor  most  used.  It  is  dissolved  in 
water,  and  added  in  small  quantity  to  the  engine  after  the  pulp 
has  come  to  color.  When  brought  into  contact  with  bleach  liquor, 
the  following  reaction  occurs  :  — 

2(Ca(C10)2)  +  Na&O,  +  H20  =  2  CaS04  +  2  HC1  +  2  Nad, 

in  which  the  products  are  calcium  sulphate,  or  Pearl  Hardening, 
hydrochloric  acid,  and  common  salt.  Every  409  parts  of  active 
bleaching-powder  (35  per  cent.)  here  requires  248  parts  of  the 
hyposulphite.  This  is  the  reaction  as  usually  given  and  as  it 
commonly  occurs,  but  if  the  solutions  employed  are  very  dilute, 
the  decomposition  may  take  place  in  another  direction,  viz. :  — 

Caf  C10)2+  4  Na&O,  +  H2O  =  2  Na&O,  +  2  NaCl  +  2  NaOH  +  CaO. 


284  THE  CHEMISTRY  OF  PAPER-MAKING. 

The  use  of  hyposulphite  of  soda  is  open  to  the  objection  that 
the  products  of  either  of  the  above  reactions  are  nearly  as  preju- 
dicial in  the  paper  as  the  traces  of  bleach  which  might  remain 
after  washing.  If  more  than  a  small  quantity  of  antichlor  is  used, 
the  stock  should  afterwards  be  washed.  Sodium  sulphite,  Na2SO3, 
which  neutralizes  the  bleach  after  the  manner  shown,  — 


Ca(C10)2  +  2  NazSOg  =  CaSO4  -f  NaSO4  +  2  NaCl, 

has  been  used  abroad  as  a  substitute  for  the  hyposulphite,  and  is 
to  be  preferred,  and  not  only  because  it  is  more  efficient  weight 
for  weight,  but  because  the  products  of  its  action  are  less  likely 
to  have  an  injurious  effect  upon  the  paper,  in  case  they  are  not 
thoroughly  washed  out. 

Calcium  sulphite,  CaSO8  ,  is  used  to  a  considerable  extent  in  this 
country  under  the  name  of  Hosford's  Antichlor.  It  is  found  in 
the  market  in  the  form  of  a  very  fine,  smooth  powder,  nearly  white, 
and  showing  a  granular  structure  under  the  microscope.  On 
account  of  the  slight  solubility  of  the  salt,  the  reaction,  — 

€a(C10)j  4  2  CaS03  =  CaCl,  4  2  CaSO4, 

upon  which  its  value  depends,  proceeds  rather  slowly.  Any  excess 
of  this  antichlor  goes  into  the  paper  to  make  weight,  and  is  quite 
unobjectionable,  except  possibly  in  the  presence  of  very  delicate 
colors.  The  chloride  of  calcium  resulting  from  the  reaction  should, 
however,  be  removed  by  washing,  since,  when  present  even  in 
traces,  it  hastens  the  deterioration  of  the  paper.  Kellner  has 
advocated  the  addition  of  sulphite  of  lime  to  the  stock,  on  the 
ground  that  it  retards  the  aging  and  yellowing  of  papers  which 
have  been  heavily  sized  with  rosin,  or  which  contain  ground  wood. 
The  ordinary  sulphite  liquor  used  in  the  manufacture  of  wood 
pulp  forms,  as  will  be  readily  inferred  from  the  last  two  paragraphs, 
a  very  efficient  antichlor.  As  the  sulphites  are  in  solution,  the 
action  of  the  liquor  is  rapid,  and  its  use  in  many  cases  tends  to 
brighten  the  color,  though  this  effect  is  not  likely  to  be  permanent. 
Any  considerable  excess  of  the  liquor  is  to  be  avoided  unless  the 
pulp  is  to  be  afterwards  washed,  as  otherwise  there  is  danger  that 
traces  of  free  sulphuric  acid  may  be  formed  in  the  paper  through 
the  oxidation  of  the  bisulphite,  and  cause  a  rapid  deterioration 
in  the  strength  of  the  fibre,  besides  corroding  the  wire  and  rusting 
the  dryers  of  the  paper-machine. 


BLEACHING.  285 


The  mixture  of  calcium  thiosulphate  and  polysulphide,  made  by 
boiling  together  milk  of  lime  and  sulphur,  has  been  proposed  as  a 
cheap  and  effective  antichlor ;  but  since  a  considerable  proportion 
of  free  sulphur  is  precipitated  by  the  action  of  the  bleach  upon 
the  mixture,  its  use  is  not  to  be  recommended.  The  sulphur  is 
left  in  the  fibre  in  such  a  finely  divided  condition  as  to  be  slowly 
changed  into  sulphuric  acid  by  ordinary  atmospheric  influences, 
and  as  a  result  there  is  a  gradual  conversion  of  the  fibre  into  the 
brittle  hydrocellulose.  The  free  sulphur  is  also  likely  to  cause 
rotting  of  the  wire  through  formation  of  metallic  sulphides. 

Lunge  recommends  the  use  of  hydrogen  peroxide  as  an  antichlor. 
It  removes  the  oxygen  from  the  hypochlorite,  and  is  at  the  same 
time  decomposed  into  water  and  free  oxygen.  Its  use  offers  none 
of  the  objections  which  can  be  urged  against  the  other  antichlors 
on  account  of  the  products  which  they  leave  in  the  paper,  and 
the  durability  of  the  bleached  stock  is  rendered  more  assured. 
The  reaction  is  a  noteworthy  one,  inasmuch  as  it  furnishes  an  in- 
stance of  one  powerful  oxidizing  agent  being  reduced  through  the 
action  of  another  oxidizing  agent. 

In  many  cases,  and  especially  in  sulphite  pulp,  which  before 
bleaching  contains  a  considerable  proportion  of  only  slightly  modi- 
fied incrusting  matter,  it  -is  much  easier  to  obtain  a  cream  or 
slightly  yellow  tone  in  the  bleached  fibre  than  the  pure  white, 
which  is  desired.  This  color  is  largely  due  to  the  yellow  tint 
of  the  insoluble  chlorinated  compounds  formed  by  the  action  of 
bleach  upon  the  ligno-cellulose,  and  on  that  account  is  an  evidence 
of  the  presence  in  the  pulp  of  compounds  which  considerably 
impair  its  quality,  aside  from  the  mere  question  of  color.  It  is 
possible  by  the  judicious  use  of  blue,  the  color  complementary  to 
yellow,  to  mask  this  undesirable  appearance  of  the  pulp  and 
greatly  improve  its  apparent  color.  This  practice  is  not  uncommon 
in  case  of  pulp  which  is  offered  for  sale,  but  the  improvement  in 
color  is  quite  fictitious  and  serves  only  to  disguise  the  true  quality 
of  the  pulp.  In  extreme  cases  the  sophistication  is  apparent  to 
the  eye,  or  may  be  detected  at  once  by  the  bluish  tint  observed  on 
looking  through  a  sheet  of  the  suspected  pulp.  If  the  quantity 
of  blue  used  has  been  more  carefully  proportioned,  its  presence 
may  nevertheless  be  usually  detected  by  rolling  the  suspected 
sheet  into  a  tube  and  looking  through  it,  or  by  looking  into  a  fold 
of  the  pulp  as  into  a  partly  opened  book.  In  each  of  these  cases 


286  THE  CHEMISTRY  OF  PAPER-MAKING. 

.the  blue  is  intensified  by  the  multiple  reflections  of  the  light 
before  reaching  the  eye. 

Even  when  a  yellow  tint  is  not  apparent  in  the  bleached  fibre, 
it  often  contains  an  appreciable  quantity  of  chlorinated  cellulose. 
We  have  found  in  bleached  sulphite  pulp  of  good  color  between 
5  and  6  per  cent,  of  this  material.  The  same  pulp,  after  warming 
to  100°  F.  for  eight  hours  with  weak  bleach  solution,  contained 
10  per  cent,  of  the  chlorinated  cellulose,  an  increase  of  about 
5  per  cent,,  while  a  portion  treated  with  the  same  bleach  solution 
in  the  cold  for  the  same  time  showed  an  increase  of  the  chlorinated 
cellulose  of  only  2  per  cent. 

To  show  still  further  the  action  of  warm  bleach  solution,  we 
treated  a  sample  of  pure  cellulose  with  dilute  bleach  solution  at 
a  temperature  of  140°  F.  for  four  hours.  The  sample,  after 
thorough  washing  and  drying,  showed  a  loss  of  6^  per  cent.,  while 
the  dried  sample  was  found  to  contain  19  per  cent,  of  chlorinated 
cellulose  soluble  in  very  weak  soda.  One-quarter  of  the  cellulose, 
then,  in  this  experiment  had  been  changed,  and  nearly  one-tenth 
(allowing  for  the  increase  of  weight  by  the  chlorine  absorbed) 
actually  burned  up  and  dissipated. 

Many  of  the  highly  lignified  bast  fibres,  like  jute,  manila,  and 
hemp,  are  especially  liable  to  chlorination,  and  fail  to  come  to  good 
color  when  subjected  to  the  ordinary  process  of  bleaching.  These 
compounds  of  chlorine  with  the  fibre  substance  range  in  color 
from  bright  yellow  to  orange,  and  develop  a  magnificent  magenta 
when  treated  with  a  solution  of  bisulphite  of  soda.  They  are 
readily  soluble  in  alkalies,  and  may  be  removed  from  the  fibre  by 
treatment  with  a  1  to  2  per  cent,  solution  of  soda-ash. 

Besides  the  chlorination  mentioned,  which  is  a  danger  that  care 
will  usually  avoid,  there  is  always  in  bleaching  a  slight  oxidation 
of  the  external  layers  of  cellulose  which  is  sufficient  to  affect  the 
chemical  relations  of  the  fibre  itself  to  certain  coloring-matters. 
This  change  of  relationship  is  mainly  due,  in  the  case  of  paper 
pulp,  to  the  formation  of  a  superficial  layer  of  oxycellulose,  which 
has  a  marked  affinity  for  the  basic  coloring-matters  and  the  power 
of  withdrawing  them  from  their  solutions.  If  the  oxidation  ex- 
tends into  the  substance  of  the  fibre  it  occasions  a  considerable 
loss  of  strength. 


BLEACHING.  287 


The  following  analysis,  made  by  ourselves,  may  be  taken  as 
indicative  of  the  composition  of  well-bleached  fibre :  — 

ANALYSIS  OF  FILTER  PAPER. 

(Schleicher  and  SchulVs  JVo;  597.} 

Per  oeut. 

Moisture,  loss  at  100°  C 5.26 

Mineral  matter,  ash  ..     . 0.37 

Hydrocellulose,  etc.  (soluble  in  alcohol)    .     .  0.73 

Cellulose 93.69 

.  Lignin,  etc none 

100.05 

We  have  obtained  the  following  analytical  and  experimental 
figures  from  two  samples  of  unbleached  spruce  pulp  made  by  the 
sulphite  process.  A  was  a  sample  of  what  may  be  called  normal 
pulp,  whereas  it  had  been  found  impossible  in  practice  to  bleach 
B  to  anything  like  good  color.  The  latter  sample  contained,  as 
will  be  noted,  0.34  per  cent,  of  waxy  material  removable  by  carbon 
disulphide,  and  our  examination  showed  that  to  this  material  the 
difficulty  which  had  been  experienced  was  mainly  due.  The 
material  contained  sulphur  in  combination,  and  was  most  probably 
formed  during  boiling  by  the  action  of  the  liquor  upon  some  of 
the  constituents  of  the  wood.  The  presence  in  the  liquor  of  the 
higher  and  easily  decomposed  sulphur  acids  is  known  to  com- 
plicate the  boiling  process,  and  it  is  not  impossible  that  this  waxy 
material  was  the  result  of  abnormal  reactions  thus  occasioned. 
The  objectionable  substance  was  in  any  case  so  modLied  by  the 
bleaching  as  to  be  removable  by  washing  with  very  weak  acid  and 
alkali,  and  the  color  of  the  sample  thus  washed  was  beyond 

criticism. 

A.  2*. 

Moisture 7.00  7.89 

Organic  matter  removed  by  bleaching     ......  2.35  3.39 

Waxy  material  removed  by  carbon  disulphide   after 

bleaching  and  drying —  0.34 

Hydrocellulose,  gums,  etc.,  remaining  in  bleached  pulp, 

soluble  in  dilute  caustic  potash  (1  per  cent)    .     .     .  2.76  2.17 
Mineral  matter  removed  by  weak  acid  (1  per  cent.  HC1)  0.60  1.10 
Mineral  matter  remaining  in  bleached  pulp  after  treat- 
ment with  potash  and  acid     .     .    ^ 0.22  0.27 

Cellulose  •.    .<........ 87.12  84.83 

100.05  99^99 


288 


THE  CHEMISTRY  OF  PAPER-MAKING. 


A  B 

Apparent  loss  in  bleaching 1.40        2.31 

Mineral  matter  added  by  bleaching  process      ....      0.95        1.08 

Actual  organic  matter  lost  in  bleaching 2.35        3.39 

Chlorination  of  fibre  in  bleaching none       none 

Bleaching-powder    (35  per  cent,    available    chlorine) 

consumed    .......   V. 16.90      18.80 

Time  of  bleaching  experiment,  4J-  hours  at  about  50°  C. 

Color  obtained good       bad 

(greenish) 

Pulp,  after  bleaching  and  treatment  with  potash  and 
acid,  contained :  — 

Cellulose 99.78      99.73 

Mineral  matter  (ash) 0.22        0.27 

100.00    100.00 

Ash  of  pulp  as  received 0.82  1.3T 

Ash  of  bleached  pulp  before  treatment  with  potash  and 

acid  (original  moisture  basis) 1.79  2.51 

Color  of  bleached  pulp  after  purification  with  potash 

and  acid good       good 

O'Neill  gives  the  following  interesting  results  of  experiments 
made  to  determine  the  tensile  strength  of  cotton  threads  before 
and  after  bleaching,  by  measuring  the  strain  required  to  break  the 
thread.  The  calico  experimented  on  was  of  good  quality,  and  had 
sixteen  to  eighteen  threads  to  the  |~inch;  the  length  taken  for 
testing  varied  from  0.25  inch  to  3.1  inch. 


Average  weight  required  to  break 
a  single  thread. 


Before  bleaching.     After  bleaching. 


No.  1  cloth,  weft  threads 
No.  1      "      warp      " 

No.  2      "        "          «« 
No.  3      "        "          " 


1714  grains 
3140      " 
3407      " 
3512       " 


2785  grains 
2920      " 
3708      " 
4025      " 


It  is  seen,  says  the  author  quoted,  that  in  two  cases  out  of 
three,  the  warp  threads  are  stronger  after  bleaching  than  before* 


BLEACHING.  289 


and  in  one  case  a  little  weaker.  All  that  can  be  safely  concluded 
from  numerous  trials  made  is,  that  the  tensile  strength  of  the 
cotton  yarn  is  not  injured  by  a,  careful  but  complete  bleaching, 
and  probably  it  may  be  strengthened  by  the  wetting  and  pressure 
causing  a  more  complete  and  effective  binding  of  the  separate 
cotton  hairs  or  filaments,  the  twisting  together  of  which  makes 
the  yarn. 

There  is  a  generally  received  opinion  among  the  manufacturers 
of  soda  pulp  that  it  is  impossible  to  bleach  their  stock  to  good 
color,  if  more  than  a  slight  trace  of  alkali  remains  in  the  fibre. 
The  difficulty  is  usually  attributed  to  the  presence  of  the  alkali 
itself,  but,  as  excellent  results  in  bleaching  may  be  obtained  by 
the  use  of  an  alkaline  solution  of  sodium  hypochlorite,  this  is 
evidently  an  error.  The  trouble  is  really  due  to  the  presence  of 
the  organic  matter  in  the  small  amount  of  black  liquor  still 
remaining  in  the  pulp,  and  with  which  the  alkali  is  associated. 

We  have  made  a  large  number  of  experiments  in  elucidation  of 
this  point,  and  find  that  a  small  proportion  of  such  soluble  organic 
matter  remains  in  even  very  well  washed  brown  pulp  as  taken 
from  the  mill.  Forty  grammes  dry  of  such  well  washed  poplar 
pulp  required  for  its  complete  extraction  3800  cc.  of  distilled  water 
before  the  percolate  failed  to  give  a  test  for  organic  matter,  and  the 
total  amount  of  chlorine  consumed  by  the  organic  matter  extracted 
amounted  to  0.053836  grammes.  When  the  washing  has  been  well 
conducted  at  the  mill,  we  find  a  remarkably  close  agreement  in 
the  figures  which  represent  the  amount  of  organic  matter  still 
remaining  in  the  pulp  of  different  mills.  The  amount  of  chlorine 
consumed  by  the  organic  matter  extracted  per  100  grammes  dry 
pulp  closely  approximating  0.135  grammes. 

In  order  to  determine  the  effect  of  this  small  quantity  of  soluble 
organic  matter  upon  the  bleaching  process,  we  have  in  a  number 
of  cases  percolated  several  successive  lots  of  pulp  with  the  same 
water,  after  which  another  portion  of  pulp  was  mixed  up  with  the 
percolate,  and  bleached  in  the  usual  way.  For  comparison,  a 
quantity  of  pulp  similar  to  the  last  was  beaten  up  with  distilled 
water  and  similarly  bleached.  We  give  the  results  of  one  experi- 
ment. Four  lots  of  brown  poplar  pulp,  amounting  in  all  to  266 
grammes  dry,  were  successively  percolated  with  the  same  water. 
Two  fresh  lots  of  pulp  were  then  taken,  each  containing  88.6 
grammes  of  dry  pulp.  Lot  A  was  beaten  up  with  water,  while  lot  B 


290  THE  CHEMISTRY  OF  PAPER-MAKING. 

was  beaten  up  with  the  percolate  previously  obtained.  A  bleached 
readily  to  good  color  in  two  and  one-half  hours,  with  a  total 
chlorine  consumption  of  1.5954  grammes.  B^  at  that  time,  was 
far  from  being  bleached,  and  at  the  end  of  five  hours  B  was  still 
inferior  to  A  in  color,  although  fairly  well  bleachedv  The  chlorine 
consumed  by  B  amounted  to  2.1493  grammes.  That  is,  the  organic 
matter  extracted  from  266  grammes  of  dry  pulp  was*  sufficient  so 
to  retard  the  bleaching  process  that  more  than  double  the  time  was 
required,  while  there  was  an  increase  in  the  chlorine  consumption 
of  28.07  per  cent. 

Where  unfiltered  water,  or  water  highly  colored  by  organic 
matter  in  solution,  is  used  in  bleaching,  an  appreciable  quantity 
of  bleaching-powder  is  required  to  bleach  the  water,  and  it  will 
sometimes,  especially  in  case  of  water  colored  by  peat,  be  almost 
impossible  to  make  the  water  entirely  clear  and  colorless.  This 
organic  matter  has,  moreover,  the  same  effect  in  retarding  the 
bleaching  of  the  pulp  to  color  as  that  in  brown  liquor.  We  have 
made  a  number  of  experiments  to  determine  the  quantity  of 
bleach  consumed  by  different  waters,  and  give  a  few  of  our  results 
in  the  chapter  on  "Water. 

Cloudman  has  patented  an  apparatus  especially  adapted  to  the 
better  bleaching  and  washing  of  soda  pulp,  which  is  thoroughly 
sound  in  principle,  and  which  has  proved  itself  very  economical 
and  efficient  in  practice.  It  is  shown  in  Fig.  64,  in  which  are 
sub-figures  1  and  2.  Fig.  1  shows  the  apparatus  in  plan,  and  Fig.  2 
is  a  vertical  longitudinal  section  of  a  modified  arrangement  of  two 
chests  in  line  with  one  another,  and  with  the  conveyor  for  the 
material  to  be  bleached  and  the  passage  through  which  the  pulp 
passes  from  the  top  of  one  chest  into  the  bottom  of  the  next  chest 
shown  in  the  plane  of  section. 

The  apparatus  consists  of  a  series  of  chests  fitted  with  agitators, 
washing-drums,  and  conveyors  /.  The  bleach  liquor  is  sent 
through  the  series  in  one  direction,  while  the  pulp  is  carried 
through  in  the  opposite  direction.  The  strong  liquor  entering  the 
chest  marked  a4  acts  at  first  upon  the  pulp  which  has  been  nearly 
brought  to  color  by  contact  with  the  weaker  liquor  in  the  other 
chests,  while  the  nearly  exhausted  liquor  entering  the  first  chest  a, 
expends  its  remaining  strength  upon  the  brown  pulp  which  first 
passes  into  this  chest. 

Each  chest  is  provided  with  an  inlet  passage  5,  the  pulp  entering 


BLEACHING. 


291 


the  chest  near  the  bottom  through  this  passage,  and,  together 
with  the  pulp,  the  bleaching  agent  which  has  previously  passed 
through  the  other  chests  of  the  series,  is  introduced  so  that  both 
enter  together  at  the  lower  portion  of  the  first  chest  a  of  the  series. 


FIG,  64. — CLOUDMAN  APPARATUS  FOR  WASHING  AND  BLEACHING. 

A  continuous  flow  of  pulp  and  bleach  liquor  is  maintained,  so  that, 
at  each  moment,  the  lower  portion  entering  tends  to  displace 
that  which  has  already  entered,  thus  causing  the  mixture  to  rise 
gradually  upward  from  the  bottom  to  the  top  of  the  chest.  By 


292  THE  CHEMISTRY  OF  PAPER-MAKING. 

means  of  the  conveyor  and  washing-drum  at  the  top  of  the  chest 
the  pulp  and  liquor  are  partially  separated  when  they  reach  the 
top. 

The  brown  pulp  enters  at  the  bottom  of  the  first  chest  a,  through 
the  inlet  passage  5.  As  it  reaches  the  top  of  the  chest  it  is  raised 
by  the  conveyor  /,  and  discharged  into  the  top  of  the  inlet  pas- 
sage 5,  leading  to  the  chest  #2.  It  passes  through  this  chest,  and 
is  similarly  raised  and  discharged  by  the  next  conveyor  in  the 
inlet  to  the  chest  a3.  From  the  top  of  this  chest  it  is  again  raised 
by  the  third  conveyor  and  discharged  into  the  inlet  to  the  chest  a4. 
The  bleached  pulp  is  taken  by  the  conveyor  from  the  top  of  this 
chest  and  is  discharged  through  the  outlet  h.  Simultaneously 
with  the  above  operations  the  strong  bleach  liquor  has  been 
passing  through  the  chest  in  reverse  order,  entering  through  the 
inlet  #4,  and  being  finally  discharged  as  waste  through  the  outlet  e, 
leading  from  the  chest  #,  into  which  the  brown  pulp  has  entered. 
The  passage  of  the  bleached  liquor  through  the  series  is  effected 
by  means  of  the  washing-drums  </,  which  partially  separate  the 
liquor  from  the  pulp,  and  which  discharge  into  the  inlet  opening 
of  the  chest  next  preceding  the  one  from  which  the  liquor  came. 
In  this  way,  as  bleaching  progresses,  the  pulp  meets  stronger 
and  stronger  bleach  liquor ;  while,  as  the  proportion  of  available 
chlorine  in  the  liquor  decreases,  the  proportion  of  coloring-matter 
present  in  the  pulp  upon  which  the  liquor  is  then  acting  increases. 
This  is,  of  course,  a  reversal  of  the  conditions  obtaining  in  the 
usual  methods  of  bleaching,  where,  as  it  becomes  increasingly 
difficult  to  oxidize  the  last  portion  of  coloring-matter,  there  is  less 
and  less  available  chlorine  present  for  the  purpose. 

Use  of  Acid.  —  The  careful  use  of  small  quantities  of  hydro- 
chloric or  sulphuric  acid  in  bleaching  quickens  the  process  by 
liberating  hypochlorous  acid,  which  is  much  more  energetic  in  its 
action  than  bleaching-powder  itself.  The  acid  is  best  added  after 
the  pulp  has  nearly  come  to  color,  and  should  in  all  cases  be 
diluted  with  several  times  its  volume  of  water,  and  should  then 
be  poured  into  the  chest  or  engine  in  a  slow  stream.  A 
small  amount  of  acid  is  as  effective  as  a  larger  quantity;  its 
action  is  more  gradual,  and  there  is  less  danger  of  chlorination 
of  fibre  and  consequent  loss  of  color.  The  first  addition  of  acid 
neutralizes  the  lime  present  and  decomposes  the  hypochlorite  to 
form,  if  hydrochloric  acid  is  used,  chloride  of  calcium  and  free 


BLEACHING.  293 


hypochlorous  acid.  The  hypochlorous  acid  gives  up  its  oxygen 
and  is  reduced  to  hydrochloric  acid,  which  reacts  with  a  fresh 
quantity  of  the  hypochlorite  as  before,  and  the  cycle  of  reactions 
continues  until  all  of  the  hypochlorite  has  been  decomposed. 
A  small  amount  of  hypochlorous  acid  is  thus  continuously  liber- 
ated, but  never  enough  to  injure  the  fibre  unless  an  excessive 
quantity  of  the  stronger  acid  has  been  added.  It  is  best  to  add 
the  acid  in  several  successive  portions,  and  to  stop,  if  any  strong 
odor  of  hypochlorous  acid  persists. 

Lunge  recommended,  several  years  ago,  the  use  of  small  quan- 
tities of  acetic  acid  in  bleaching,  in  preference  to  the  mineral  acids, 
as  its  action  is  safer,  while  the  amount  required  is  so  small  that 
no  objection  can  be  made  on  account  of  cost.  The  acid  has  only 
recently  been  brought  to  the  attention  of  the  trade  in  a  commercial 
way,  b't  its  use  in  the  bleaching  of  paper  stock  is  now  growing 
rapidly.  About  one  gallon  of  the  commercial  acid  is  added  to  a 
1000-pound  engine  with  the  bleach  liquor.  It  is  stated,  although 
the  grounds  for  the  claims  are  hardly  apparent,  that  when  used  in 
connection  with  acetic  acid,  the  amount  of  bleach  may  be  reduced 
one-third,  with  the  production  of  a  cleaner  and  whiter  half  stuff. 
The  results  obtained  in  bleaching  jute  in  this  manner  are  said  to 
be  especially  good, 

Treating  Jute.  —  Jute  and  similar  materials  derive  their  chief 
value  as  paper  stock  from  the  fact  that  the  short  ultimate  fibres  are 
bound  together  in  the  plant  into  filaments  of  great  length  and 
strength.  In  order  that  the  stock  may  lend  itself  to  the  mechanical 
operations  involved  in  the  formation  of  a  sheet  of  paper,  it  is  nee- 
essaiy  that  these  filaments  be  separated  and  partially  broken  down, 
but  the  methods  of  treatment  are  so  regulated  as  to  stop  consider- 
ably short  of  such  complete  removal  of  the  incrusting  matter  as 
would  determine  the  separation  of  the  ultimate  fibres.  The 
bleaching  of  such  stock  is  therefore  rarety  carried  beyond  a  good 
cream. 

Jute  butts,  as  received  at  the  mill,  usually  contain  from  12  to 
18  per  cent,  of  moisture.  They  are  first  cut  into  three  or  four 
slabs  or  pieces,  and  violently  •"  thrashed "  for  a  few  minutes  to 
remove  the  coarser  particles  of  adhering  dirt.  A  further  cutting 
and  dusting  follows,  after  which  the  stock  is  ready  for  boiling. 
The  loss  in  weight  caused  by  this  preliminary  treatment  usually 
varies  from  7  to  10  per  cent. 


294  THE  CHEMISTRY  OF  PAPER-MAKING. 

The  stock  is  boiled  in  rotariqs  for  about  twelve  hours  with  milk 
ot  lime  sufficient  to  rather  more  than  half  fill  the  rotary.  The 
proportion  of  lime  varies  from  200  to  300  Ibs.  per  ton  of  stock. 
In  some  mills  the  pressure  is  never  allowed  to  exceed  15  Ibs.,  while 
in  others  it  is  raised  to  20  or  even  30  Ibs.  The  stock,  after  dump- 
ing from  the  rotary,  is  commonly  allowed  to  remain  on  the  floor 
for  twenty-four  to  thirty-six  hours  to  "temper,"  or  soften,  and  is 
then  thoroughly  washed  in  an  engine  to  remove  ail  dirt  and  lime. 

Bleaching,  properly  so-called,  is  done  in  the  engine,  the  chloride 
of  lime  being  generally  added  as  powder  in  the  proportion  of  from 
10  to  20  per  cent.,  according  to  the  color  desired  and  the  thorough- 
ness of  the  previous  treatment.  4  or  5  per  cent,  of  acid  alum  is 
sometimes  added  to  hasten  the  action  of  the  bleach,  but  in  this 
case  or  if  the  stock  is  heated,  there  is  much  danger  of  chlorinating 
the  fibre  and  forming  yellow  compounds,  which  defeat  the  object 
of  the  process.  The  stock,  after  running  two  or  three  hours  in  the 
engine,  is  often  dumped  into  drainers,  where  the  bleaching  is 
allowed  to  continue  slowly  for  about  a  week. 

Bleaching  Ground  Wood.  —  Many  paper-makers  have  ex- 
pressed a  desire  for  a  process  of  bleaching  ground  wood,  but  the 
matter  presents  several  difficulties  which  are  not  likely  to  be 
overcome.  Ground  wood  contains,  of  course,  all  the  constituents 
of  the  wood  itself,  except  the  small -proportion  which  was  soluble 
in  water.  There  is,  therefore,  in  all  such  pulp  about  50  per  cent, 
of  incrusting  matter  to  be  destroyed  by  the  hypochlorite  solution 
before  a  white  color  can  be  obtained,  and  any  process  of  true 
bleaching  would  entail  a  corresponding  shrinkage  in  the  weight 
of  the  fibre  and  an  enormous  consumption  of  bleach.  The  first 
effect  of  the  bleach  liquor  is  to  lower  the  color  of  the  pulp  to 
red  or  brown,  and  this  shade  persists  until  nearly  all  the  incrusting 
matter  has  been  destroyed. 

Although  bleaching-powder  is  practically  the  only  agent  used 
for  bleaching  paper  stock,  various  other  bleach  liquors  have  been 
proposed  from  time  to  time,  and  in  some  cases  these  possess  ad- 
vantages which  would  warrant  their  introduction,  were  it  not  for 
their  greater  cost.  Among  these  liquors  are :  — 

Magnesia  Bleach  Liquor.  —  This  is  prepared  by  adding  Epsom 
salts  to  a  solution  of  ordinary  bleaching-powder,  when  calcium 
sulphate  is  precipitated  and  magnesium  hypochlorite  remains  in 
solution.  The  clear  liquor  decanted  from  the  precipitate  is  more 


BLEACHING.  295 


unstable,  but  also  more  energetic  in  its  action  than  the  liquor 
made  directly  from  bleaching-powder.  It  is  less  caustic,  and  does 
not  turn  straw,  hemp,  flax,  etc.,  brown,  as  is  done  by  hypochlorite 
of  calcium  solution.  This  liquor  is  also  known  as  Ramsay's  or 
Crouvelle's  ble aching-liquor.  A  solution  of  magnesium  hypo- 
chlorite, prepared  by  the  electrolysis  of  a  5  per  cent,  solution  of 
magnesium  chloride,  has  been  used  on  the  large  scale  by  Hermite 
in  his  electric  bleaching  process,  and  the  efficiency  claimed  for  his 
bleaching-liquor  is  undoubtedly  due  more  to  its  composition  than 
to  the  method  of  its  manufacture. 

Aluminum  Bleach  Liquor.  —  Sometimes  called  Wilson's  bleach 
liquor,  is  prepared  by  treating  a  solution  of  bleaching-powder  with 
one  of  alum.  The  reaction  is  similar  to  that  which  takes  place  in 
the  preparation  of  the  magnesium  hypochlorite :  that  is,  there  is 
a  precipitation  of  sulphate  of  lime,  while  the  liquor  consists  of 
aluminum  hypochlorite  in  solution.  This  liquor  is  exceedingly 
efficient,  and  the  aluminum  chloride  which  results  from  its  decom- 
position is  said  to  prevent  the  fungoid  and  other  growths  which 
sometimes  appear  as  black  specks  upon  bleached  fibre.  If  this 
chloride  is  allowed  to  remain  in  the  paper,  however,  it  hastens 
the  deterioration  and  yellowing  of  the  .sheet.  Aluminum  hypo-, 
chlorite  is  formed,  of  course,  when  alum  is  added  to  the  paper- 
engine,  as  is  often  the  case  in  the  ordinary  process  of  bleaching ; 
and  where  the  alum  used  is  a  neutral  one,  the  increased  rapidity 
of  the  bleaching  action  is  due  to  the  aluminum  hypochlorite  which 
hits  been  formed-  With  an  acid  alum  there  may  be,  in  addition, 
cbme  liberation  of  free  hypochlorous  acid. 

Zinc  Bleach  Liquor. —  By  substituting  zinc  sulphate  for  the 
alum  just  mentioned,  a  solution  of  zinc  hypochlorite  is  formed. 
This  bleaches  very  rapidly,  splitting  up  first  into  zinc  oxide  and 
hypochlorous  acid.  If  the  sulphate  of  zinc  is  added  to  the  bleach 
liquor  in  the  paper-engine,  zinc  oxide  and  sulphate  of  lime  remain 
in  the  pulp.  Zinc  hypochlorite  is  sometimes  called  Varreutrapps' 
bleaching-salt. 

In  certain  English  mills  and  bleacheries  which  are  in  close 
proximity  to  plants  manufacturing  bleaching-powder,  there  is 
often  used  a  bleach  solution  which  is  prepared  by  passing  chlorine 
directly  into  milk  of  lime.  In  this  way  an  excellent  liquor  is 
prepared,  which  is  even  more  efficient  than  that  smade  up  from 
bleaching-powder.  It  is  not  improbable  that,  with  the  development 


296  THE  CHEMISTRY  OF  PAPER-MAKING. 

of  the  electrolytic  processes  for  the  decomposition  of  salt,  this 
liquor  may  find  a  use  in  this  country  in  plants  which  are  con- 
veniently located  to  a  source  of  chlorine. 

Among  the  bleach  liquors  which  are  at  present  rarely  or  never 
used  may  be  mentioned  Eau  de  Javelle  and  Eau  de  Labarraque, 
The  former  is  made  by  passing  chlorine  into  a  solution  of  potassium, 
carbonate,  and  the  latter  by  similarly  treating  a  solution  of  car- 
bonate of  soda.  In  either  case,  the  absorption  of  gas  is  continued 
until  there  is  a  slight  effervescence^  due  to  liberation  of  carbonic 
acid.  If  the  caustic  alkalies'  are  substituted  for  the  carbonates, 
similar  but  not  identical  liquors  are  prepared. 

It  has  already  been  pointed  out  that  the  hypochlorites  vary 
with  respect  to  the  ease  with  which  they  are  decomposed  in  the 
presence  of  coloring-matter,  and  the  rapidity  of  the  bleaching 
action  therefore  varies  in  the  different  cases.  The  hypochlorites 
of  alumina,  zinc,  and  magnesia,  are  considerably  more  rapid  in  their 
action  than  hypochlorite  of  lime.  Hypochlorite  of  soda  is  slowest 
of  all,  but  when  very  slightly  acidulated  the  action  is  as  rapid  as 
in  case  of  any  of  the  other  hypochlorites  named. 

Liquid  Chlorine.  —  The  advent  of  this  material  as  a  bleaching 
agent  affords  a  curious  example  of  the  manner  in  which  the 
development  of  a  process  sometimes  follows  lines  which  apparently 
bring  one  back  at  last  to  the  point  of  starting,  although  in  reality 
the  new  point  reached  is  on  a  higher  plane.  The  early  methods 
of  gas  bleaching  were  displaced  by  the  simpler  and  more  manage- 
able processes  involving  the  use  of  hypochlorites,  and  it  now  see»ns 
not  improbable  that  the  economies  and  improvements  recently 
introduced  in  the  methods  of  manufacture  and  transport  of  chlorine 
in  its  elementary  form  may  re-establish  gas  bleaching. 

The  gas  prepared  from  common  salt,  either  by  the  well-known 
chemical  methods  or  by  the  later  ones  which  involve  the  use  of 
electricity,  is  first  dried  and  then  brought  to  the  liquid  state  by 
cooling  and  compression.  The  liquefied  chlorine  has  a  yellow 
color  which  is  almost  orange,  and  its  specific  gravity  is  1.6602  at 
—  80°  C. ;  at  0°  0.  it  is  1.4689 ;  at  19°  C.,  1.4156 ;  at  40°  G.,  1.3490 ; 
and  at  77°  C.,  1.216.  The  coefficient  of  expansion  is  .00203 
between  15°  0.  and  20°  0.,  and  what  is  called  the  critical  tempera- 
ture of  the  gas  is  146°  C.,  i.e.,  at  any  temperature  higher  than  the 
one  given,  it  is  impossible  by  any  increase  of  pressure  to  condense 
the  gas  into  the  liquid. 


BLEACHING. 


297 


The  liquefaction  is  usually  effected  in 
stout  wrought-iron  drums,  one  form  of 
which  is  shown  in  Fig.  65.     This  drum 
is  provided  with  two  valves;  and  when 
a  quantity  of  gaseous  chlorine  is  desired, 
the  drum  is  set  up  vertically,  and  the 
protecting-cap  A  is  unscrewed.   The  plug 
By  or  B',  of  one  of  the  valves,  is  then 
removed,    and    replaced     by    a    screw- 
coupling   0.      To  this  coupling  is   best 
connected  a  lead  pipe  for  conveying  the 
gas  to  the  point  of  use.     It  is  necessary 
to  open  the  valve  very  slowly,  as  other- 
wise a  sudden  rush  of  gas  may  burst  the 
conveying-pipes.     The  conversion  of  the 
liquefied   chlorine    to  the  gaseous  form 
is  attended  by  so  great  an  absorption  of 
heat  that  the  outside  of  the  drum  becomes 
heavily  coated  with  frost,  in  which  case, 
if  a  considerable  amount  of  gas  must  be 
drawn  off,  it  becomes  necessary  to  raise 
the  temperature  of  the  drum,  either  by 
placing  it  in  moderately  warm  water,  or 
by  wrapping  it  in  hot  cloths.     The  gas 
may  be  used  for  bleaching  in  the  drainer, 
or  it  may   be  absorbed  in  water  or   in 
milk  of  lime.     The  latter  method  gives 
a  liquor  which  is  considerably  more  rapid 
and  efficient  in  its  action  than  any  liquor 
made  from  bleaching-powder.    Those  who 
are  interested  in  this  new  phase  of  bleach- 
ing will  find  an  interesting  and  exhaus- 
tive paper  on  the  subject  by  R.  Kneitsch, 
in  the  "  Annalen  der  Chemie,"  No.  259, 
page  100.    He  gives  in  the  following  table 
the  pressure  which  the  gas  exerts  on  the 
inner  surface  of  the  cast-iron  drums  in 
which  it  is  shipped.  It  will  be  noted  that 
pressures  are  only  for  the  ordinary  temper- 
atures which  lie  between  0°  and  40°  C. 


298  THE  CHEMISTRY  OF  PAPER-MAKING. 


Temperature 
in^C. 

0 

Pressure  in 
Atmospheres. 

3.660 

Temperature 
in  °C. 

+  21.67 

Pressure  in 
Atmosphere*. 

6.960 

+   9.62 

4.885 

+  29.70 

8.652 

+  13.12 

5.433 

+  33.16 

9.470 

f-      +20.85 

6.791 

+  38.72 

10.889 

Use  of  Oxygen.  —  The  brothel's  Brin,  who  have  successfully 
attacked  the  problem  of  producing  oxygen  on  a  commercial  scale, 
have  made  a  large  number  of  experiments  with  a  view  to  the  use 
of  the  gas  as  an  auxiliary  agent  in  bleaching  with  chloride  of 
lime.  It  does  not  appear  that  the  high  hopes  at  first  entertained 
for  the  process  have  been  realized,  although  under  favorable  con- 
ditions, and  where  the  stock  to  be  bleached  was  thoroughly  cookfxi, 
some  saving  of  bleaching-powder  was  shown.  Contrary  to  what 
was  claimed  at  the  time  by  the  advocates  of  oxygen,  no  improve- 
ment was  noticed  in  either  the  feel,  appearance,  or  felting  qualities 
of  the  resulting  bleached  stock.  Since  these  first  experiments 
were  made,  the  price  of  oxygen  has  been  materially  lowered,  until 
to-day  it  can  be  made  for  0.05  cent  per  cubic  foot  under  favorable 
circumstances.  It  is  now  claimed  by  those  who  control  this 
process  that  in  bleaching  esparto,  with  ordinary  bleach  liquor  plus 
oxygen,  the  quantity  of  bleach  required  can  be  reduced  in  the 
proportion  of  2  to  1.25,  so  that,  in  a  case  where  a  ton  of  stock 
requires  ordinarily  224  Ibs.  of  35  per  cent,  bleach,  the  use  of  200 
cubic  feet  of  oxygen  saves  no  less  than  84  Ibs. 

Mr.  Thorne,  an  expert  in  the  use  of  oxygen  for  bleaching,  claims 
that  results  can  be  obtained  with  oxygen  which  cannot  be  secured 
through  the  use  of  compressed  air,  and  explains  this  rather  curious 
phenomenon  by  Ihe  theory  that  the  large  amount  of  inert  nitrogen 
which  necessarily  accompanies  the  oxygen  when  compressed  air 
is  used,  carries  away  some  oxygen  and  chlorine  before  the  latter 
has  time  to  act. 

So  far  as  we  are  aware,  no  thoroughly  satisfactory  theory  has 
been  advanced  to  explain  the  action  of  oxygen  when  used  in  this 
way,  for  oxygen  in  the  gaseous  form  has  no  especial  bleaching 
power. 

Ozone  Bleach.  —  The  Fahrig  electrostatic  process  for  the  pro- 
duction of  ozone  on  a  commercial  scale  has  placed  this  powerful 
bleaching  agent  in  a  position  which  encourages  its  advocates  to 
claim  that  it  may  yet  successfully  compete  with  the  hypochlorites 


BLEACHING.  299 


in  the  bleaching  of  cellulose.  It  is  already  used  with  excellent 
effect  for  bleaching  water ;  20  grains  per  1000  gallons  is  sufficient, 
it  is  claimed,  to  give  a  good  result,  and  it  is  already  being  used 
upon  a  considerable  scale  as  a  bleaching  and  oxidizing  agent  in 
various  lines  of  industry,  which  are,  however,  foreign  to  our 
subject.  It  is  usually  employed  in  the  form  of  a  1  per  cent,  solu- 
tion, although  solutions  containing  7  per  cent,  or  8  per  cent,  of 
ozone  are  sometimes  made. 

Hydrogen  peroxide  is  closely  similar  to  ozone  in  its  action,  and 
is  also  attracting  some  attention  as  a  possible  substitute  for  hypo- 
chlorites.  It  is  employed  in  the  form  of  a  weak  solution,  to  which 
magnesia  is  sometimes  added. 

Sulphurous  Acid  Bleach.  —  The  bleaching  action  of  sulphurous 
acid,  as  has  been  already  pointed  out  elsewhere,  differs  essentially 
from  that  of  the  various  oxidizing  agents  which  have  been  con- 
sidered. In  those  methods  of  bleaching  which  involve  oxidation, 
the  coloring-matters  are  split  up  into  much  more  simple  oxidation 
products,  which  are  themselves  colorless.  Sulphurous  acid  in  only 
a  few  cases  bleaches  by  the  destruction  of  the  coloring-matter,  so 
that  whatever  value  it  possesses  as  a  bleaching  agent  depends 
mainly  upon  its  property  of  combining  with  the  coloring-matter 
to  form  colorless  compounds,  from  which  the  unchanged  coloring- 
matters  may  be  again  liberated  by  the  action  of  a  stronger  acid, 
or  merely  by  continued  exposure  to  atmospheric  influences.  Many 
of  the  brightly  colored  flowers,  for  example,  may  be  bleached  by 
exposure  to  the  gas;  but  if  they  are  then  dipped  in  very  weak 
sulphuric  acid,  the  original  color  is  restored.  Wool  and  other 
animal  fibres  are  generally  bleached  by  means  of  sulphurous  acid, 
and  the  color  reappears  when  the  acid  combines  with  the  alkali 
of  the  soap  used  in  washing. 

In  the  best  unbleached  sulphite  fibre  the  coloring-matters  are 
merely  masked,  and  more  chloride  of  lime  is  required  to  bleach 
such  fibre  than  is  needed  in  the  case  of  pulp  which,  through  the 
use  of  higher  temperatures,  has  had  the  in  crusting  matter  more 
thoroughly  removed,  although  its  color  is  much  poorer.  The  first 
effect  of  bleaching-powder,  as  is  well  known,  is  to  cause  a  marked 
lowering  of  color,  as  the  first  products  of  the  oxidation  are 
usually  more  highly  colored  than  the  original  materials.  If 
now  an  excess  of  bisulphite  liquor  is  added  to  the  pulp,  the 
latter  immediately  becomes  nearly  or  quite  white,  not  on  account 


300  THE  CHEMISTRY  OF  PAPER-MAKING. 

of  any  true  bleaching  action,  but  because  the  sulphurous  acid  arrests 
the  process  of  oxidation  and  conceals  the  coloring-matters  by 
combining  with  them.  The  subsequent  addition  of  an  excess  of 
bleaching-powder  solution  oxidizes  the  acid  and  restores  the  color 
as  the  first  step  in  the  resumption  of  the  true  bleaching  process. 
It  is  therefore  evident  that  any  bisulphite  liquor  or  sulphite  of 
lirne  which  remains  in  sulphite  pulp,  as  a  result  of  imperfect 
washing,  consumes  its  equivalent  of  hypochlorite,  if  the  pulp  is 
subsequently  bleached,  and  adds  proportionately  to  the  cost  of 
bleaching. 


8IZ1XG  AND  LOADING.  301 


CHAPTER  V. 

SIZING   AND   LOADING. 

THE  infinite  number  of  small  spaces  which  exist  within  and 
between  the  fibres  of  a  sheet  of  unsized  paper,  cause,  by  capillary 
action,  a  rapid  spreading  and  absorption  of  any  liquid  with  which 
the  paper  may  come  in  contact.  It  is  to  this  property  that  blot- 
ting paper  owes  its  value,  and  there  are  a  few  other  applications 
which  require  the  use  of  an  unsized  or  so-called  "  water-leaf " 
paper.  Most  of  the  uses  to  which  paper  is  put,  however,  imply 
its  contact  with  ink  in  one  form  or  another,  and  it  thus  becomes 
necessary  to  so  fill  up  the  pores  and  coat  the  fibres  with  some 
material  which  shall  offer  sufficient  resistance  to  the  passage,  of 
fluid  to  prevent  the  spreading  of  the  ink.  This  object  is  accom- 
plished by  the  various  methods  of  sizing  which  we  propose  to 
consider  in  this  chapter. 

The  extent  to  which  the  sizing  must  be  carried,  and  the  nature 
of.  the  sizing  agents  employed,  depends  upon  the  purpose  for  which 
the  paper  is  to  be  used.  Writing  papers  which  are  to  come  into 
contact  with  very  fluid  writing  inks,  require  a  much  more  perfect 
sizing  than  do  printing  papers  for  use  with  a  thick  and  viscid 
printing  ink.  The  division  may  be  earned  much  farther,  for 
while  it  is  the  object  of  some  printing  papers  to  retain  the  ink 
almost  wholly  upon  the  surface  of  the  sheet,  such  papers  as  are 
used  for  other  work  in  which  quick  absorption  and  rapid  drying 
of  the  ink  is  necessary  must  have  sufficient  capillary  power  or 
"  pull,'*  as  it  is  called,  to  accomplish  these  results. 

In  the  days  of  hand-made  paper  practically  the  only  material 
used  for  sizing  was  gelatine,  which  was  called  animal  sizing  from 
its  source,  and  tub  sizing  from  its  method  of  application,  the  size 
being  formerly  contained  in  a  tub  into  which  the  paper  was  dipped 
by  hand. 

With  the  advent  of  machine-made  paper,  and  the  application  of 
the  material  to  printing  purposes,  other  methods  of  sizing  carne 
into  use,  until  now  the  number  of  substances  which  have  been  more 


302  THE  CHEMISTRY  OF  PAPER-MAKING. 

or  less  successfully  adapted  to  the  purpose  is  considerable.  Prac- 
tically, however,  all  sizing  is  still  done  either  with  gelatine  or 
rpsin.  The  materials  used  for  rosin  sizing  are  applied  to  the 
beaten  stuff  either  in  an  engine  or  chest,  and  this  form  of  treat- 
ment is  therefore  known  as  engine  sizing. 

Properties  of  Gelatine.  —  Pure  gelatine  is  a  colorless,  odorless, 
almost  transparent  substance,  having  an  insipid  taste  and  being 
usually  quite  brittle.  Its  toughness,  however,  varies  with  its 
source.  It  softens  and  shrinks  on  heating,  and  gives  off  an  un- 
pleasant nitrogenous  odor  on  burning.  It  is  insoluble  in  cold 
water,  but  swells  and  absorbs  three  or  four  times  its  weight  of  the 
liquid.  In  hot  water  it  is  freely  soluble,  and  the  strong  solution 
upon  cooling  sets  to  a  firm  clear  jelly.  A  firm  jelly  is  hardly 
formed  unless  the  solution  contains  about  7  per  cent,  of  gelatine. 
With  the  best  material  even  so  little  as  1  per  cent,  gives  a  gelati- 
nous mass  on  cooling. 

This  power  of  gelatinizing  is  said  to  be  destroyed  by  over-heat- 
ing the  solution,  or  if  the  solution  is  frequently  heated  and  cooled. 
The  most  conspicuous  property  of  gelatine,  and  the  one  on  which 
its  value  in  the  manufacture  of  leather  depends,  is  found  in  its 
formation  of  an  insoluble  compound  with  tannic  acid.  Gelatine  is 
also  precipitated  from  its  solution  by  alcohol,  and  is  insoluble  in 
ether  and  oils,  but  is  dissolved  by  concentrated  sulphuric  acid  in 
the  cold.  Alum  does  not  precipitate  it  although  it  thickens  the 
solution.  If  alkali  is  added  to  the  mixture  in  sufficient  quantity 
a  precipitate  is  formed  containing  gelatine  and  a  basic  sulphate. 

The  purest  commercial  form  of  gelatine  is  isinglass  prepared 
from  the  swimming  bladders  of  certain  fish,  notably  the  sturgeon. 
Glue  is  a  comparatively  crude  form  of  the  material,  and  is  made 
by  boiling  down  scraps  of  hide,  horn,  and  hoof.  Bones  yield  a 
similar  but  inferior  product.  The  yield  from  raw-hide  is  about 
50  per  cent. 

The  production  of  glue  in  a  commercial  form  involves  several 
distinct  operations,  but  the  preparation  of  size  is  simpler  partly 
because  the  raw  material  as  purchased  by  the  paper-maker  has 
already  undergone  the  treatment  with  lime,  and  partly  because  he 
» only  'heeds  the  glue  solution,  and  therefore  does  not  prepare  a 
solid  glue.  The  scraps  received  at  the  mill  are  soaked  for  several 
days  in  water,  which  is  changed  from  time  to  time.  Sometimes  the 
washing,  is  finished  in  drums  or  other  form  of  washing  apparatus 


SIZING  AXD  LOADING.  303 

in  which  thorough  agitation  may  be  secured.  Thorough  washing 
is  very  important  in  order  to  remove  traces  of  blood  and  any  acid 
or  lime  remaining  from  the  previous  treatment  to  which  the  skins 
have  been  subjected.  Arsenic,  usually  in  the  form  of  sulphide,  is 
also  sometimes  present,  it  being  brought  into  the  skins  by  certain 
de-hairing  processes.  The  washed  pieces  are  next  boiled  with 
water,  either  in  a  tank,  which  may  be  lined  with  lead  or  copper,  or 
else  in  a  jacketed  iron  or  copper  vessel.  Whatever  the  form  of  the 
vessel  it  is  always  fitted  with  a  false  bottom. 

The  mixture  is  then  heated  up  to  a  temperature  varying  from 
150°  to  180°  F.,  with  the  character  of  the  material  under  treatment, 
and  in  about  twelve  hours  extraction  is  completed.  Any  grease 
which  is  present  will  have  come  to  the  top  of  the  liquid,  and  must 
be  carefully  removed  or  otherwise  kept  out  of  the  size.  The  solu>- 
tion  is  cleared  from  suspended  impurities  and  dirt  either  by  set- 
tling or  nitration. 

Alum  is  added  to  the  size  partly  as  a  preservative,  and  partly 
because  it  is  thought  to  render  the  gelatine  somewhat  more  effi- 
cient as  a  sizing  agent.  The  first  effect  of  the  addition  of  the 
alum  is  to  thicken  up  the  gelatine  solution  until  it  becomes  very 
stiff,  but  curiously  enough  this  is  corrected  by  the  addition  of  a 
further  quantity  of  alum.  Arsenite  of  soda  is  sometimes  added 
as  a  preservative,  but  its  use  must  be  condemned  on  account  of  the 
poisonous  nature  of  the  material. 

In  the  process  of  animal  sizing  on  the  machine,  which  is  now 
practically  the  only  way  in  which  this  form  of  size  is  applied  in 
this  country,  the  web  of  paper  is  led  through  a  trough  nlied  with 
the  size  and  to  and  from  which  a  constant  circulation  of  the  liquid 
is  maintained  in  order  to  prevent  its  becoming  too  cool  for  use. 
The  drying  of  animal  size  in  papers  is  a  matter  of  nicety.  If  the 
best  results  are  to  be  obtained,  it  is  necessary  that  the  drying  be 
conducted  slowly  and  at  very  moderate  temperature.  The  com- 
moner way  in  the  preparation  of  writing  papers  is  to  subject  the 
sized  paper  after  cutting,  to  a  process  of  loft  drying,  in  which  the 
sheets  are  suspended  on  poles  in  a  loft  which  is  kept  warm  by 
steam  pipes.  By  this  slow  drying,  the  glue  is  gradually  brought  in 
great  part  to  the  surface  of  the  sheet,  where  its  presence  is  most 
required.  Cheaper  grades  of  paper  are  sometimes  dried  on  the 
machine,  but  in  this  case  a  large  number  of  skeleton  driers  are  sub- 
stituted for  the  steam  drums  which  are  ordinarily  used  as  driers. 


804  THE  CHEMISTRY  OF  PAPER-MAKING. 

Each  of  these  skeleton  driers  has  within  it  a  fan  for  keeping  up 
the  circulation  of  the  air,  and  the  total  number  of  such  driers  may 
be  thirty-five  or  more. 

It  is  of  the  utmost  importance  that  the  size  be  entirely  free  from 
grease  and  acid  ;  the  former  is  liable  to  make  unsightly  streaks  and 
spots,  while  even  traces  of  acids  are  likely  to  affect  delicate  colors 
and  cause  deterioration  of  the  paper.  Animal  size  is  sometimes 
used  in  moderate  amount  directly  in  the  engine,  but  its  value  at 
this  point  is  doubtful,  and  in  the  absence  of  any  substances  which 
will  precipitate  the  gelatine  the  greater  portion  of  it  is  lost  in  the 
wash  water. 

Engine  Sizing. —  We  have  already  made  reference  on  page  138 
to  the  more  prominent  properties  of  rosin.  Its  use  in  size  depends 
upon  its  acid  character  by  virtue  of  which  it  forms  soaps  with  the 
various  metallic  oxides,  and.  of  course  most  readily  with  potash 
or  soda.  Its  salts,  which  are  those  of  the  various  acids  which 
occur  in  rosin,  are  collectively  called  resinates.  The  resinate  of 
soda,  which  at  present  most  concerns  us,  is  made  by  boiling  rosin 
with  a  moderately  strong  solution  of  soda-ash  or  soda  crystals,  and 
is  soluble  in  water.  All  resinates  of  metals  other  than  those  of 
the  alkalis,  are  for  the  most  part  insoluble.  The  older  theory  of 
engine  sizing  is,  that  after  the  size  has  been  diluted  with  water 
and  mixed  with  the  stuff  it  is  precipitated  as  resinate  of  aluminum 
upon  the  addition  of  alum,  and  that  this  alum  soap  is  the  true 
sizing  agent,  which  by  coating  over  the  fibres  prevents  the  absorp- 
tion and  spreading  of  liquid  after  the  paper  has  been  dried.  The 
saponiiieation  of  rosin  in  the  preparation  of  size  is  rarely  complete, 
and  some  free  rosin  is  present  in  nearly  all  size.  In  some  samples 
of  white  size  as  much  as  25  per  cent,  of  the  rosin  may  be  present 
as  free  rosin  in  a  very  fine  state  of  subdivision.  Commercial 
rosin  contains  also  from  6  to  8  per  cent,  of  unsaponifiable  matter. 

According  to  the  later  theory  of  rosin  sizing,  for  which  we  are 
in  large  measure  indebted  to  the  researches  and  conclusions  of  Dr. 
Wiirster,  the  precipitate  produced  by  the  addition  of  alum  consists 
in  the  main  of  free  rosin  in  a  very  fine  state  of  division  and  mixed 
with  a  small  proportion  of  resinate  of  aluminum.  It  is  the  view 
of  Dr.  Wiirsteif  and  many  other  chemists  who  have  studied  the 
matter,  that  the  sizing  effect  is  due  solely  to  the  free  rosin?  the 
resinate  of  alumina  being  quite  inactive.  Engine  sizing,  accord- 
ing to  this  view,  consists  merely  in  mixing  very  finely  divided 


SIZING  AND  LOADING.  305 

rosin  with  the  fibres,  and  then  causing  it  to  adhere  and  penetrate 
by  the  heat  of  the  driers.  We  are  ourselves  disposed  to  adhere 
to  the  older  view,  for  if  free  rosin  alone  is  needed,  equally  good 
results  should  be  obtained  in  sizing  by  the  substitution  of  sulphuric 
acid  for  the  alum  usually  employed.  Our  own  results  and  those 
of  Dr.  Wiirster  indicate  that  such  is  not  the  case,  but  Lunge  is 
said  to  have  obtained  good  results  by  the  use  of  sulphuric  acid 
without  alum.  The  true  theory  may  perhaps  lie  between  these 
two  extremes,  and  define  the  office  of  the  alumina  as  that  of  fixing 
the  rosin  upon  the  fibres. 

Preparation  of  Rosin  Size.  —  Nearly  every  mill  has  its  own 
receipt  for  preparing  rosin  soap  for  use  in  sizing,  but  except  as  to 
proportions  the  general  method  of  procedure  is  about  the  same  in 
all  cases.  The  powdered  or  finely  broken  rosin  is  boiled  in  an 
alkaline  solution  in  an  iron  kettle,  preferably  heated  by  a  steam 
coil,  although  sometimes  live  steam  is  used.  The  darker  colored 
rosin  is  believed  to  be  the  best,  and  as  we  think  with  good  reason, 
since  it  has  been  distilled  at  a  higher  temperature,  and  therefore 
contains  less  pitchy  matter  than  the  lighter  grades.  At  the  time 
when  practically  all  soda  was  made  by  the  LeBlanc  process,  soda 
crystals  were  generally  used,  because  of  their  greater  purity  and 
even  composition.  At  present  58  per  cent.  Solvay  soda-ash  is 
almost  universally  employed,  and  it  is  undoubtedly  the  best 
material  to  use.  The  common  practice  in  this  country  calls  for 
quantities  of  soda-ash,  which  range  from  20  to  40  per  cent,  on  the* 
weight  of  the  rosin  taken. 

Beadle,  who  has  obtained  the  best  results  in  sizing  by  the  use  of 
size  containing  26  per  cent,  free  rosin,  recommends  as  the  result 
of  a  large  number  of  trials,  the  use  of  1  Ib.  of  soda-ash  to  every 
7.65  Ibs.  of  win,  or  for  1300  Ibs.  of  rosin,  170  Ibs.  of  soda-ash 
and  200  gals,  of  water,  the  whole  to  be  boiled  for  seven  hours 
and  then  made  to  the  volume  of  225  gals,  by  addition  of  water. 
Size  made  by  the  above  receipt  contained  :  — 

Per  cent. 

Combined  rosin    .........  40.59 

Free  rosin 14.37 

Combined  soda 6.72 

Free  soda 1.34 

During  the  boiling  of  size,  considerable  carbonic  acid  is  evolved 
unless  caustic  soda  is  used,  but  the  general  experience  has  been 


306.  THE  CHEMISTRY  OF  PAPER-MAKING. 

that  equally  good  results  are  not  obtained  with  this  material.  The 
frothing  ''flue  to  liberation  of  carbonic  acid  when  soda-ash  is  used, 
can  generally  be  kept  down  if  the  sides  of  the  kettle  are  not 
unduly  heated,  and  for  this  reason  where  the  steam  jacket  is  used 
it. should  only  cover  the  bottom  of  the  kettle.  In  case  the  froth- 
ing becomes  very  violent,  it  may  be  checked  by  adding  a  little 
cold  water  through  the  sprinkler  of  a  watering-pot,  but  even  when 
the  water  is  thus  showered,  it  is  apt  to  cause  the  formation  of 
clots  and  make  the  size  lumpy. 

The  amount  of  water  used  in  making  size  is  a  matter  of  impor- 
tance. With  too  much  water  the  size  sinks  to  the  bottom  with 
the  dirt,  whereas  the  aim  of  the  size-maker  should  be  to  keep  the 
solution  of  such  density  that  the  size  will  float,  while  the  dirt 
sinks. 

New  size  is  apt  to  make  size  spots,  and  it  is,  therefore,  custom- 
ary to  keep  a  supply  ahead,  and  to  draw  for  use  upon  that  which 
is  at  least  a  week,  and  better,  two  or  three  weeks  old. 

The  following  are  our  analyses  of  good  average  size  as  made  by 

mills  in  this  country :  — 

A.  B. 

Water 39.70  40.62 

Free  rosin    ......      8.54  7.22 

Dry  size 51.76  52.16 

Tallow  is  sometimes  boiled  up  in  small  amounts  with  the  rosin 
and  is  thought  to  improve  the  feel  and  finish  of  the  sheet,  but  iu 
the  manner  and  small  quantity  in  which  it  is  used  its  value  in 
these  directions  is  doubtful. 

Action  of  Light  on  Rosin  Size,  —  It  has  been  known  for  a 
long  time  that  both  rosin  and  ground  wood  undergo  some  rather 
obscure  changes  on  exposure  to  light  and  air,  and  that  these 
changes  were  among  the  most  important  factors  in  causing  the 
deterioration  of  paper  by  age.  The  subject  has  been  investigated 
somewhat  carefully  by  Herzberg.  Five  kinds  of  engine-sized 
paper,  the  size  of  which  was  proved  normal  by  testing,  were 
exposed  to  direct  sunshine  and  air  for  a  period  of  two  months ; 
they  were  then  tested,  and  exposed  for  another  similar  period.  At 
the  end  of  the  second  exposure,  four  samples  out  of  the  five  were 
no  longer  fit  to  write  upon.  These  were  made  of  linen  and  cotton 
rags*  some  being  with  and  some  without  ground  wood  pulp  and 
straw.  The  fifth  sample  was  made  of  ground  wood  and  sulphite, 


SIZING  AND  LOADING.  80? 

and  gave  an  ash  of  13.5  per  cent.  This  was  almost  unaffected  so 
far  as  the  size  was  concerned,  although  the  color  was  more  altered 
than  in  case  of  any  of  the  others.  The  exact  nature  of  the  change 
which  takes  place  in  rosin  when  exposed  in  this  finely  divided 
state  to  light,  is  not  known,  but  Herzberg  has  proved  that  the 
change  is  due  to  light,  rather  than  to  the  gases  composing  the 
atmosphere,  since  in  other  of  his  experiments,  papers  similarly 
exposed  in  tubes  with  oxygen  and  sulphuric  acid  were  not 
affected  so  long  as  they  were  kept  in  diffused  daylight.  A  piece 
of  rosin  kept  for  some  time  in  direct  sunlight  loses  its  vitreous 
appearance  and  becomes  covered  with  yellow  powder. 

Use  of  Alumiiiatc  of  Soda.  —  Certain  advantages  have  been 
claimed  for  a  method  of  preparing  rosin  size  in  which  the  saponi- 
fication  of  the  rosin  is  effected  by  means  of  aluminate  of  soda, 
instead  of  carbonate  of  soda  or  caustic  soda,  as  is  usually  the  case. 
Aluminate  of  soda  is  a  compound  in  which  the  alumina  plays  the 
part  of  a  weak  acid  and  enters  into  combination  with  the  soda. 
From  this  compound  alumina  may  be  precipitated  by  the  addition 
of  acid  or  many  salts. 

The  rosin  soap  is  prepared  by  boiling  rosin  in  the  usual  manner, 
except  for  the  substitution  of  aluminate  of  soda  for  the  customary 
alkali.  One  part  by  weight  of  aluminate  of  soda  is  dissolved  in/ 
four  times  its  weight  of  water  and  added  to  two  parts  by  weight 
of  rosin.  It  is  only  necessary  to  have  sufficient  alkali  present  to 
thoroughly  saponify  and  hold  the  rosin  in  solution,  and  the  pro- 
portion just  given  may  be  greatly  varied  so  long  as  this  condition 
is  met.  The  soap  is  added  to  the  pulp  in  tfye  beating  engine  in 
the  usual  manner,  and  is  decomposed  with  precipitation  of  tho 
rosin  and  alumina  upon  the  addition  of  a  soluble  salt  of  magne- 
sium such  as  chloride  or  a  sulphate.  Chloride  of  calcium  may 
also  be  used  to  advantage,  or  even  ordinary  alum,  and  the  results 
in  the  latter  case  are  said  to  be  better  with  size  prepared  after  the 
present  method  than  are  attainable  through  the  use  of  a  common 
rosin  size.  The  strength  of  the  solution  used  for  the  precipita- 
tion may  be  conveniently  one  part  of  the  salt  dissolved  in  twenty 
parts  of  water,  but  it  is  unnecessary  to  adhere  closely  to  this  for- 
mula. Where  the  magnesia  salts  are  used  the  base  is  precipitated 
at  the  same  time  together  with  the  rosin  and  alumina. 

Casein  Sizing.  —  Casein  is  a  nitrogenous  substance  occurring 
in  milk  and  closely  resembling  animal  albumen  in  its  composition 


THE  CHEMISTRY  OF  PAPER-MAKING. 


and  properties.  One  thousand  parts  of  normal  milk  contain,, 
according  to  Fownes,  48.20  parts  of  casein.  A  closely  similar 
body  is  found  in  the  vegetable  kingdom,  notably  in  pease,  beans 
and  lentils,  and  is  called  vegetable  casein  or  legumiu.  Liebig, 
indeed,  considers  the  two  materials  identical,  but  doubt  has  been 
thrown  upon  this  view  by  later  investigators.  The  name  casein  is 
derived  from  the  Latin  one  for  cheese,  which  is  formed  in  large 
part  of  casein,  and  which  bears  a  close  resemblance  to  it. 

Casein  is  prepared  by  coagulating  the  milk  with  dilute  acid 
or  with  rennet,  and  washing  the  coagulum  first  with  water,  then 
with  water  containing  a  little  acid,  and  finally  with  pure  water 
again.  It  may  then  be  brought  down  by  diying  to  a  friable 
mass,  and  usually  appears  in  commerce  as  a  dry  granular  powder 
of  yellowish  tinge.  It  dissolves  readily  in  very  weak  alkaline 
solutions  and  is  precipitated  by  many  salts  and  especially  by  alum. 
The  solution  has  not  been  used  to  any  extent  in  this  country  for 
sizing  paper,  but  experiments  in  this  direction  have  been  made  by 
a  number  of  German  mills  whose  experience  has  been  sufficiently 
favorable  to  warrant  a  trial  of  the  material  by  American  paper- 
makers.  Its  use  depends  .upon  the  property  possessed  by  casein 
of  forming  a  bulky,  gelatinous,  insoluble  compound  with  alum 
which  adheres  to  the  fibres  and  subsequently  dries  upon  them, 
leaving  the  pores  well  filled. 

The  casein  in  the  form  of  a  20  per  cent,  to  50  per  cent,  solution  is 
commonly  added  to  the  engine  just  as  rosin  size  would  be,,  or  it  may 
be  mixed  with  the  size  in  any  desired  proportion.  In  either  case 
alum  is  afterwards  added  to  effect  the  precipitation  as  in  case  ot 
rosin  size.  Paper  sized  with  casein  is  said  to  be  much  more  elastic 
than  that  sized  with  rosin.  Practically  alltof  the  casein  goes  into 
the  sheet  Paper  so  sized  has  an  especially  good  fe$l  and  readily 
takes  a  high  finish.  Casein  size  also  lessens  the  objectionable  dust 
which  often  comes  from  papers  carrying  a  large  amount  of  mineral 
matter,  and  the  percentage  of  filler  retained  is  greater  than  with 
rosin  size. 

The  most  serious  objection  which  has  been  raised  against  this 
material  as  a  sizing  agent,  is  that  it  is  very  liable,  unless  properly 
prepared  and  handled,  to  impart  an  unpleasant  odor  to  the  paper. 

Silicate  of  Soda.  - —  This  material  has  been  used  from  time  to 
time  by  mills  which  desired  to  obtain  a  very  hard  sized  paper 
which  should  rattle.  It  is  commonly  received  in  the  form  of  a 


SIZING  AND  LOADING.  309 

clear,  very  heavy  liquid,  containing  about  50  per  cent,  of  the  sili- 
cate dissolved  in  water.  It  is  strongly  caustic  and  may  be  used 
fur  preparing  size  in  place  of  the  carbonate  usually  employed,  or 
any  desired  quantity  may  be  mixed  with  the  size  itself  or  added 
directly  to  the  engine.  The  addition  of  alum  determines  the  for- 
mation of  a  bulky,  gelatinous  precipitate  of  hydrated  silicic  acid 
which  is  very  similar  in  appearance  to  precipitated  alumina.  The 
same  precipitation  is  brought  about  by  the  addition  of  acid  to 
the  engine,  but  this  procedure  is  liable  to  bring  the  silica  down 
in  a  gritty  or  sandy  condition  in  which  it  is  likely  to  cause 
trouble  in  various  ways,  and  especially  by  leaving  the  surface  of 
the  sheet  dusty.  The  only  important  advantage  which  the  use  of 
silicate  of  soda  offers,  is  that  reproduces  a  harder  paper  and  its  use 
is  in  this  country  confined  in  the  main  to  mills  making  writing 
papers. 

Alum. — We  have  already  pointed  out  (Part  I.,  page  77,)  that 
the  term  alum  as  employed  in  paper-making  has  come  to  refer 
almost  entirely  to  sulphate  of  alumina,  and  we  shall  now  use  the 
word  in  this  restricted  sense.  The  use  of  alum  in  paper-making 
is  due  primarily  to  the  fact  that  when  a  solution  of  alum  comes  in 
contact  with  one  of  rosin  size,  there  is  formed  a  bulky,  adhesive, 
gelatinous  precipitate,  .composed  of  alumina  and  rosin,  which 
adheres  to  the  fibres  and  dries  down  to  a  sort  of  water-repellent 
varnish.  Other  things  being  equal,  the  value  of  an  alum  for 
the  purposes  of  paper-making  is  usually  held  to  vary  with  the  per- 
centage of  alumina  present,  but  this  is  by  no  means  a  conclusive 
indication  of  the  sizing  power.  The  accompanying  table  brings 
out  the  great  variations  which  appear  in  the  composition  of  com- 
mercial alums,  and  the  sizing  power  of  the  several  samples  is  influ- 
enced by  many  factors  other  than  the  mere  percentage  of  alumina. 
It  will  be  noted  in  reference  to  these  analyses  that  in  a  well-made 
alum  the  proportion  of  material  insoluble  in  water  is  rarely  above 
0.50  per  cent.,  and  is  often  much  below  this  figure.  A  much 
higher  percentage,  such  as  appears  for  instance  in  Samples  VI., 
VIII.,  X.,  and  XIV.,  generally  indicates  that  the  original  raw 
material  has  not  been  thoroughly  broken  down  by  the  acid.  Such 
alums  are  apt  to  contain  considerable  free  acid,  and  they  find 
their  chief  use  in  bleaching  or  as  a  coagulant  in  the  purification  of 
water.  They  are  only  adapted  for  sizing  in  case  of  the  cheap- 
est papers.  The  alumina  in  these  analyses  varies  from  11.64 


810 


THE  CHEMISTRY  OF  PAPER-MAKING. 


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cipitated  by 
the  alum)  . 


SIZING  AND  LOADING.  311 

per  cent,  in  Sample  XII.,  to  22.37  per  cent,  in  Sample  IX.,  but 
there  is  no  corresponding  variation  in  the  sizing  power.  Sample 
IX.  is  a  very  basic  alum,  and  it  is  doubtful  if  the  excess  of  alumina 
above  that  needed  to  form  the  neutral  sulphate  has  much,  if  any, 
sizing  value.  The  large  quantity  of  free  acid  in  XII.  of  course 
decomposes  its  equivalent  of  size,  and,  although  objectionable  in 
itself,  increases  the  apparent  sizing  power  of  the  alum.  The  maxi- 
mum quantity  of  size  is  precipitated  by  XVI.  with  only  17.04  per 
cent,  of  alumina  and  no  free  acid,  but  after  making  proper  allow- 
ance for  the  zinc  and  iron  present  in  both  cases,  it  appears  that 
IX.  is  made  up  more  largely  of  basic  sulphate  than  the  stronger 
XVI. 

The  deleterious  effect  of  iron  upon  color  makes  the  amount  of 
this  constituent  a  matter  of  importance  in  any  alum  intended  for 
use  in  the  paper  engine.  The  total  amount  of  iron  oxides  in  the 
samples  under  discussion  ranges  from  0.02  per  cent,  in  Sampte  I. 
to  1.23  per  cent,  in  the  low  grade  Sample  XII.,  and  these  figures 
may  be  taken  as  fairly  representing  the  extremes.  Since  the  salts 
of  the  protoxide  of  iron  are  comparatively  colorless,  it  is  the  object 
of  the  alum  manufacturer  to  convert  as  far  as  possible  all  the  iron 
present  to  the  ferrous  state.  This  may  be  effected  by  the  addi- 
tion of  metallic  zinc  which  liberates  nascent  hydrogen  as  it  goee 
into  solution  in  the  liquid  alum,  and  to  this  fact  is  due  the  pres- 
ence of  the  zinc  oxide  reported  in  certain  analyses  in  the  table. 
It  should,  however,  be  noted  in  this  connection  that  while  the 
color  of  an  alum  is  improved  by  bringing  the  iron  into  the 
ferrous  state,  it  does  not  follow  that  such  iron  is  any  the  ll&m 
objectionable,  for  it  is  rapidly  oxidized  during  the  processes  of 
paper-making. 

The  soda  which  appears  as  a  common  constituent  of  the  alums 
in  the  table  is  by  itself  without  significance  as  to  their  value  or 
character.  Its  presence  is  explained  partly  by  the  use  of  bLoap* 
bonate  of  soda  in  the  manufacture  of  porous  alums,  and  to  neutral- 
ize the  last  portions  of  acid;  but  in  some  cases  it  may  be  derivad 
from  cryolite  when  this  is  used  as  the  raw  material. 

The  proportion. of  sulphuric  acid  deserves  more  attention  than 
it  usually  receives  from  buyers  of  alum.  Free  acid,  except  on  a 
bleaching  alum,  is  objectionable  not  only  because  of  its  effect  in 
color,  but  because  it  decomposes  the  size  without  at  the  same 
time  precipitating  alumina.  If  excessive  quantities  of  a  strongly 


312  THE  CHEMISTRY  OF  PAPER-MAKING. 

acid  alum  are  used  there  is  the  further  danger  of  attacking  the 
wires  and  felts,  and  injuring  the  strength  of  the  paper  as  it  passes 
over  the  driers. 

From  our  own  point  of  view  a  neutral,  or  slightly  basic,  alum 
should  give  the  best  results  in  sizing,  but  many  paper-makers 
have  a  preference  for  a  very  basic  or  "  concentrated  "  alum.  Sam- 
ples XIII.  and  XL,  which  contain  about  the  same  amount  of  total 
acid,  may  be  taken  as  representing  the  extremes  in  the  proportion 
of  acid  to  base. 

The  amount  of  alum  used  in  sizing  ranges  in  ordinary  practice 
from  6  to  12  Ibs.  to  an  engine  carrying  500  Ibs.  A  larger  quantity 
is  sometimes  added  if  the  sizing  is  to  be  very  hard,  but  the  usual 
amount  is  about  10  Ibs.  It  is  best  to  put  the  size  in  first  and 
allow  it  to  become  thoroughly  distributed  through  the  stock  before 
the  addition  of  alum,  but  some  mills  reverse  this  process.  There 
is  danger  in  this  event  that  the  size  will  be  precipitated  in  small 
lumps,  which  come  to  the  surface  and  make  spots  in  the  paper. 
In  making  manila  paper  the  dry  alum  is  added  directly  to  the 
engine,  but  for  better  papers  a  stock  solution  is  made  up  and 
cleared  by  settling  or  straining. 

The  quantity  of  alum  used  is  always  much  in  excess  of  that 
required  to  merely  precipitate  the  size,  but  although  there  is  a  con- 
siderable waste  of  alum  in  most  mills,  good  results  in  sizing  cannot 
be  obtained  by  use  of  the  minimum  amount  of  alum  required 
by  the  size  alone.  A  moderate  proportion  of  free  alum  appears 
to  be  essential  to  good  sizing,  and  portions  of  the  alum  added 
are  neutralized  by  the  water,  by  lime  or  other  alkalis  present  in 
the  stock,  and  by  traces  of  bleach.  By  virtue  of  these  decom- 
positions the  alum  in  the  engine  has  an  important  clearing  action 
similar  to  that  which  occurs  during  its  use  in  purifying  water. 
That  is,  it  has  a  tendency  to  coagulate  or  gather  together  the  fine 
suspended  matter  of  any  kind,  such  as  particles  of  filler  or  bits  of 
fibre  which  have  been  too  finely  beaten  so  that  they  might  other- 
wise be  lost. 

Temperature  has  a  noticeable  effect  on  the  quantity  of  alum 
required,  particularly  when  ground  wood  is  used,  the  amount 
required  increasing  with  the  rise  in  temperature.  If  the  temper- 
ature of  the  contents  of  the  engine  exceeds  100°  F.  it  is  impossible 
to  make  a  well-sized  sheet,  even  though  a  large  excess  of  alum  be 
added. 


SIZING  AND  LOADING.  313 

Apart  from  its  value  as  a  sizing  agent  alum  performs  several 
important  offices  in  the  coloring  of  paper,  and  these  will  be  con- 
sidered in  the  chapter  on  Coloring. 

Sizing  with  Acid  Sulphites.  —  Numerous  attempts  have  been 
made  by  German  chemists  to  size  paper  by  using  bisulphite  liquor 
in  place  of  alum  to  effect  the  decomposition  of  the  rosin  soap. 
This  decomposition  with  precipitation  of  rosin  can  easily  be 
brought  about  in  this  way,  the  extra  acid  combining  with  the 
soda  and  setting  free  the  rosin.  When  a  lime  liquor  is  used 
there  is  thus  formed  sulphite  of  soda  and  sulphite  of  lime.  As 
the  last-named  compound  is  insoluble,  it  serves  to  increase  the 
proportion  of  filler  in  the  sheet.  This  method  of  sizing  is  very 
cheap,  and  it  is  claimed  by  Kellner  to  have  the  important  advan- 
tage, when  applied  to  papers  containing  ground  wood,  of  prevent- 
ing or  retarding  very  much  the  loss  of  color  which  usually  takes 
place  in  such  papers  with  age.  This  conclusion  is  rendered  some- 
what doubtful  by  the  researches  of  Herzberg  upon  the  action  of 
light  upon  rosin  size,  which  indicate  that  the  change  which  gives 
the  darkening  in  color  is  not  one  of  simple  oxidation.  The  addi- 
tion of  the  sulphite  liquor  has  undoubtedly  some  bleaching  action 
which  may  be  useful  in  case  of  papers  made  for  immediate  con- 
sumption, but  such  bleaching  action  is  a  very  fugitive  one.  There 
is,  moreover,  considerable  danger  that  if  too  much  of  the  liquor 
is  added  to  the  engine,  some  of  the  free  sulphurous  acid  may  be 
oxidized  to  sulphuric  acid  as  the  paper  passes  over  the  heated 
driers.  Any  such  action  at  this  point  would  not  only  rust  the 
driers,  but  would  be  apt  to  render  the  paper  brittle  through 
formation  of  hydrocellulose. 

Any  free  sulphurous  acid  in  the  stock  would  corrode  the  wire 
as  the  sheet  was  formed  on  the  machine.  Another  serious  ob- 
jection to  this  method  of  sizing  is  found  in  the  action  of  the  sul- 
phurous acid  upon  many  of  the  coloring  matters  which  might  be 
employed  with  it.  It  cannot  be  denied,  in  view  of  the  results  of 
Dr.  Kellner  and  others,  that  this  method  of  sizing,  when  properly 
controlled,  may  be  made  to  yield  good  results  at  a  comparatively 
low  cost,  but  the  process  is  one  which  is  liable  to  involve  in  serious 
difficulty  any  less  experienced  workers. 

The  Mitscherlich  Sizing  Process. —  Among  the  substances 
which  occur  in  waste  sulphite  liquors  are  certain  derivatives  of 
the  wood  which  are  more  or  less  closely  allied  to  tannic  acid, 


314  THE  CHEMISTRY  OF  PAPER-MAKING. 

and  which  possess  its  property  of  precipitating  gelatine.  Dr. 
Mitscherlich  has  turned  this. to  account  in  a  process  for  engine- 
sizing  with  glue,  and  has  made  it  a  subject  of  a  paiei/t>  In  carry- 
ing out  his  process  ordinary  glue  is  digested  at  a  temperature  of 
about  60°,  with  ten  times  its  weight  of  waste  sulphite  liquor,  until 
dissolved.  This  requires  several  hours,  and  the  mixture  should  be 
stirred  from  time  to  time.  The  solution  thus  prepared  is  then 
diluted  with  more  waste  liquor  until  the  proportion  of  liquid  to  glue 
is  about  50  to  1.  The  admixture  must  be  made  very,  gradually 
with  constant  stirring,  and  at  the  ordinary  temperature  of  the  air. 
The  glue  combines  with  the  astringent  material  of  the  liquor  to 
the  extent  of  about  60  per  cent,  of  its  own  weight,  and  is  precipi- 
tated in  flocks.  The  whole  mixture  is  then  allowed  to  stand  for 
twenty-four  hours.  The  liquor  is  then  decanted  from  the  precipi- 
tate, and  the  latter  mixed  with  a  quantity  of  water  weighing 
about  forty  times  as  much  as  the  glue  originally  taken.  A  small 
quantity  of  chalk  or  soda-ash,  or  other  substances  Capable  of 
neutralizing  the  free  acid,  is  then  added.  The  compound  of 
glue  and  astringent  matter  goes  into  solution  quickly,  and  a 
liquor  so  prepared  may  be  added  directly  to  the  engine  for 
use  in  size.  Alum,  or  a  weak  acid,  will  then  cause  the  pre- 
cipitation of  the  gelatine  compound  throughout  the  fibre,  and  the 
solution  may  be  therefore  used  when  desired  in  connection  with 
ordinary  size. 

The  process  just  described  is  a  development  of  the  one  first 
patented  by  Dr.  Mitscherlich  in  1886,  in  which  paper  was  sized  by 
.feeding  in  continuously  on  one  side  of  the  beating  engine  the 
waste  sulphite  liquor  in  a  small  stream,  while  ordinary  glue  solu- 
tion was  similarly  fed  in  on  the  other  side  of  the  engine.  As  the 
two  dilute  solutions  came  together  the  gelatine  compound  was 
precipitated,  and  the  action  was,  of  course,  continuous  as  long  as 
the  supply  was  kept  up. 

Loading.  —  The  use  of  mineral  fillers  has  come,  to  have  a  recog- 
nized and  legitimate  place  in  paper-making,  and  the  presence  of 
such  fillers  in  a  sheet  is  not  under  ordinary  circumstances  to  be 
regarded  as  evidence  of  adulteration.  They  are  used  quite  as 
much  for  their  beneficial  effect  upon  the  feel  and  finish  of  the 
paper  as  through  a  desire  to  lower  the  cost  of  production.  Many 
of  the  best  grades  of  book  paper  could  not  be  made  at  all  with- 
out the  use  of  some  filler  in  considerable  amount  to  giv.e  the 


SIZING  AND  LOADING.  "315 

smoothness  of  surface  required  to  bring  out  the  fine  lines  of 
process  cuts. 

The  materials  commonly  employed  in  this  connection  are  some 
of  the  betier  sorts  of  china  clay  or  kaolin,  ground  talc,  and 
sulphate  of  lime.  In  preparing  these  for  the  paper-maker  the  clays 
are  mixed  with  water  to  form  a  thin  cream,  which  is  then  sent 
through  long  sluice  ways  or  settling  boxes  with  riffles  to  catch  and 
retain  the  coarser  particles  which  settle  out.  The  water  is  then 
allowed  to  drain  off  from  the  finest  particles,  which  alone  are  suit- 
able for  paper-making,  and  the  clay  comes  to  the  market  in  the 
form  of  fairly  dry  lumps  of  moderate  size. 

The  ground  talc  is  usually  not  floated,  but  it  is  put  instead 
through  a  fine  bolting  cloth.  Sulphate  of  lime  when  used  in  the 
form  of  ground  gypsum  is  similarly  treated. 

The  value  of  the  filling  material  for  use  in  paper-making  is 
dependent  upon  several  factors,  those  of  most  importance  being 
color  and  fineness.  The  suitability  of  the  material  is  also  largely 
determined  by  its  specific  gravity,  as  this  of  course  affects  the  rate 
at  which  the  particles  of  filler  settle „  The  retention  is  thus  likely 
to  be  low  in  case  of  a  very  heavy  filler,  and  the  paper  is  likeiy 
to  be  thin  for  weight.  Solubility  in  water  to  any  considerable 
extent  of  course  unfits  a  material  for  use  as  a  filler.  Even  the 
slight  degree  of  solubility  possessed  by  sulphate  of  lime  is  suffi- 
cient to  cut  down  the  retention  appreciably. 

A  filler  for  use  in  high-grade  papers  should  be  almost  entirely 
free  from  either  grit  or  mica,  since  the  former  is  apt  to  mark  the 
calender  rolls,  while  the  shiny  specks  of  the  latter  are  very  appar- 
ent in  the  finished  sheet. 

Clays. — These  are  formed  by  the  weathering  and  disintegration 
of  feldspathic  rocks.  The  presence  of  mica  indicates  that  the 
source  of  the  clay  was  granite.  With  a  moderate  quantity  of 
water  they  form  a  sticky  plastic  mass,  with  more  or  less  soapy 
feel.  Chemically  considered  they  are  essentially  silicate  of  alu- 
mina. Since  the  value  of  clay  for  the  uses  of  paper-making  is  so 
largely  determined  by  color,  only  those  sorts  like  the  china  clays, 
in  which  the  content  of  iron  is  small,  are  suitable.  The  com- 
position of  the  clays  in  general  use  by  paper-makers  is  given 
below,  and  their  microscopical  appearance  is  shown  in  Figs.  66, 
67.  and  68. 


316 


THE  CHEMISTRY  OF  PAPER-MAKING. 


ANALYSES  OF  CLAYS. 
Griffin  &  Little. 


- 

I. 

II. 

III. 

IV. 

Moisture,  loss  at  100°  C  

030 

10  15 

7  09 

9  10 

Combined  water,  volatile  at  red  heat  *    .     .     . 
Silica  (SiO2)    

12.27 

47  56 

10.77 
42  72 

11.27 
43  50 

12.79 
41  1C 

Alumina  (Alj03)  

38  12 

33  44 

35  48 

35  84 

0.08 

1  04 

•trace 

067 

Lime  (GaO)                                 

0  39 

1  61 

0  17 

0  42 

Magnesia  (McO)  . 

0.00 

0.16 

0.41 

o.ee 

Alkalis        

1.28 

0.11 

2.08 

100.00 

100.00 

100.00 

100.00 

Specific  gravity  of  dry  substance     ..... 

2  8626 

2  6585 

2  6461 

Grit  by  flotation  test  (per  cent.)          .         . 

065 

6  83 

0.10 

I 

Agalite.  —  This  is  a  finely  ground  talc,  and  is,  chemically,  a 
silicate  of  magnesia.  'It  has  an  especially  good  color,,  and  a  smooth, 
soapy  feel.  It  is  not  nearly  so  finely  reduced  as  clay,  and  the 
proportion  of  grit  is  mudh  larger.  It  is,  however,  retained  well 
in  the  paper,  and  large  quantities  of  it  are  used.  Its  appearance 
under  the  microscope  is  shown  in  Fig.  69. 


OF  AGALITE. 

Griffin  A  Little. 

Percent. 

Moisture  and  combined  water,  volatile 

at  red  &eat 1.40 

Silica  (Si02) 61.89 

Alumina  (A1203)      -     • 1.36 

Sesquioxide  of  iron  (Fe2O8)  .     ....  0.44 

Lime  (CaO) 4.21 

Magnesia  (MgO) .     .  30.70 


100.10 


Specific  gravity,  2.6875. 


Pearl  Hardening.  —  Crystallized  sulphate  of  lime,  CaSO4, 
2H2O,  prepared  by  precipitating  a  solution  of  calcium  chloride 
with  one  of  acid  sodium  sulphate,  or  with  dilute  sulphuric  acid, 


SIZING  AND  LOADING.  317 

has  been  largely  imported,  and  used  as  a  filler  in  the  finer  grades 
of  paper  under  the  name  of  Pearl  hardening.  Abroad  it  is  some- 
times called  Annaline.  Crown  filler  is  another  trade  name  for  the 
same  material. 

The  crystallized  sulphate  thus  prepared  is  especially  white, 
clean,  and  free  from  grit.  As  found  in  the  market,  in  moist 
lumps,  it  contains  a  considerable  percentage  of  water  in  addition 
to  thn  water  of  crystallization.  The  latter  amounts  to  20.93  per 
cent,  on  the  chemically  pure,  and  otherwise  dry,  substance ;  and 
this  combined  water  remains  with  the  filler  to  add  to  the  weight 
of  the  air-dry  paper.  We  give  the  following 

ANALYSIS  OF  PEARL  HARDENING. 

Griffln  &  Little. 

Per  cent. 

Sand,  etc.,  insoluble  in  acid None. 

Moisture      .     . 25.99 

Combined  water,  driven  off  at  red  heat  .     15.31 

Sulphate  of  lime  (CaS04) 1 57.85 

Chloride  of  calcium  (CaCl2) -.      0.79 

99.94 

Specific  gravity  of  dry  material,.  2, 3962. 

Under  the  microscope,  Fig.  70,  pearl  hardening  is  seen  to  consist 
of  minute  needle-like  crystals  which  have  somewhat  the  appear- 
ance of  short  fibres.  The  crystals  are  soluble  in  about  400  parts 
of  water,  or  to  the  extent  of  about  22  Ibs.  per  1000  gals.  This 
face,,  especially  when  the  proportion  of  filler- used  is  small,  and 
when  the  return  water  is  allowed  to  run  away,  has  a  considerable 
effect  in  cutting  down  retention. 

Ground  Gypsum  is  sometimes,  though  rarely,  used  as  a  filler. 
It  answers  to  the  same  formula  as  pearl  hardening,  CaSO4,  2H2O, 
but  in  the  grinding  its  crystalline  structure  is  broken  down,  so 
that,  in  this  regard,  it  is  little  different  from-  any  other  finely 
pulverized  mineral. 

Fibrous  Alutnine.  — -  A  new  filler,  which  has  several  important 
advantages,  baa  lately  been  put  upon  the  market  under  this  name. 

1  Equivalent  to  crystallized  sulphate  of  lime  (CaSO^  2H2O),  72.89. 


818  THE  CHEMISTRY  OF  PAPER-MAKING, 

It  is  a  fine,  smooth,  white  powder  almost  entirely  free  from  grit, 
and  has  the  following  composition :  — 

ANALYSIS  OF  FIBROUS  ALUMINE. 

Griffin  &  Little. 

Per  cent. 

Insoluble  iu  acid 0.32 

Sulphate  of  lime  (CaS04) l 82.55 

Sulphate  of  alumina  (A12(S04)8)   .     ,    .  5.92 

Sulphate  of  iron  (Fe2(SO4)3)     ,    .     .     .  0.22 

Carbonate  of  lime  (CaCO3)  .....  1.04 

Carbonate  of  magnesia  (MgCO3)    .     .     .  0.34 

Combined  water  .  9.67 


100.06 
l  Equivalent  to  crystallized  sulphate  of  lime  (CaSO4J  2H,O),  104.40. 

Examination  of  the  above  analysis  discloses  the  fact  that  the 
filler  consists  mainly  of  anhydrous  sulphate  of  lime  and  that  the 
alumina  present  is  also  combined  as  sulphate.  This  sulphate  of 
alumina  is,  therefore,,  as  readily  available  for  use  in  sizing  as  though 
it  were  so  much  alum  added  directly  to  the  engine.  Upon  agita- 
tion with  water  the  anhydrous  sulphate  of  lime  combines  with 
two  molecules  of  water  of  crystallization,  and  assumes  the  fibrous, 
crystalline  structure  which  is  shown  in  Fig.  71,  and  from  which 
the  filler  derives  its  name.  Every  100  Ibs.  of  the  sulphate  of  lime 
as  put  in  the  engine  forms  126  Ibs.  of  the  crystallized  sul- 
phate, arid  this  fact,  together  with  the  fibrous  character  of  the 
crystals,  has  an  important  bearing  upon  the  quantity  retained. 
Our  comparative  tests  have  shown  that  after  hydration  fibrous 
alumine  settles  much  more  slowly  than  other  mineral  fillers,  and 
this  not  only  aids  retention  but  ensures  a  more  even  distribution 
of  the  filler  through  the  paper.  The  sizing  power  of  100  Ibs. 
of  fibrous  alumine  is  about  equal  to  that  of  12  Ibs.  of  alum  of 
good  grade. 

Retention.  —  Fillers  are  usually  added  to  the  engine  after  the 
stock  has  been  well  beaten,  and  before  the  addition  of  the  size  and 
alum,  as  the  precipitation  of  the  size  tends  to  fix  the  filler  in  the 
fibre.  Clays  are  made  into  a  cream  with  water  and  when  intended 
for  the  better  grades  of  paper  are  strained  through  a  piece  of 
Fourdrinier  wire  before  going  to  the  engine.  Pearl  hardening  is 


SIZING  AND  LOADING-  319 

similarly  beaten  up,  although  the  straining  is  unnecessary.  Agalite 
is  put  into  the  engine  dry.  Fibrous  alumine  is  agitated  briskly  in 
a  separate  vessel  with  water  for  about  one-half  hour  to  bring  about 
the  desired  crystallization,  and  is  then  run  into  the  engine  through 
a  revolving  strainer  which  holds  back  any  of  the  larger  crystals. 

The  quantity  of  filler  retained  by  the  paper  may  vary  from  30  to 
80  per  cent,  of  that  introduced  into  the  engine.  The  higher  figure 
is  only  reached  under  exceptional  conditions,  and  a  retention  of 
50  per  cent,  is  usually  regarded  as  satisfactory.  A  number  of 
factors  influence  the  retention,  but  although  it  is  easy  to  point  out 
in  a  general  way  the  direction  of  their  effect,  it  is  impossible  to  lay 
down  rules  which  shall  apply  to  any  one  factor  while  the  others 
are  ignored.  The  kind  of  stock  and  the  thoroughness  with  which 
it  has  been  beaten  and  sized  has  much  to  do  with  the  quantity  of 
filler  left  in  the  sheet.  Slow  stuff  holds  the  filler  much  better  than 
that  which  is  "  quick  "  and  allows  the  water  to  leave  it  rapidly  on 
the  wire.  A  heavy  pull  on  the  suction-boxes  cuts  down  retention, 
and  there  is  also,  of  course,  a  heavy  loss  in  the  return  water  when 
this  is  allowed  to  run  to  waste.  This  may  amount  to  a  pound  of 
iiller  in  every  30  gallons.  Thick  stuff  and  heavy  papers  generally 
show  better  retention  than  thin  papers  or  stuff  which  is  much 
diluted,  and  the  percentage  held  varies  also  with  the  different 
fillers  and  the  quantities  used.  With  pearl  hardening,  for  example, 
the  proportion  retained  is  usually  greater  when  the  quantity  used 
is  large  than  when  it  is  inconsiderable. 

Use  of  Starch.  —  J.  Wiesner,  who  has  examined  some  hundreds 
of  ancient  papers,  finds  that  prior  to  the  13th  century  starch  was 
the  only  material  used  for  sizing.  It  is  still  used  in  small  quanti- 
ties as  a  tiller  and  is  thought  to  give  a  better  feel  and  surface  to 
the  paper.  It  is  either  boiled  up  with  the  size  or  the  boiled  paste 
may  be  added  directly  to  the  engine.  Often  the  starch  is  merely 
mixed  with  water  and  added  after  the  mineral  filler.  Its  value  is 
doubtful,  as  many  tests  prove  the  retention  to  be  extremely  low. 


320  THE  CHEMISTRY  OF  PAPER-MAKING. 


CHAPTER  VI. 

COLORING. 

THE  great  advances  in  textile-dyeing  and  color-printing 
have  resulted  from  the  application  of  modern  chemical  methods  of 
research  to  the  problems  of  the  art  have  by  no  means  found  their 
counterpart  in  the  coloring  of  paper,  which  still  remains  a  rather 
etude  and  empirical  operation.  Men  whose  knowledge  of  the  dif- 
ferent coloring-matters  and  the  methods  for  their  development  or 
application  is  in  any  way  coextensive  with  that  of  the  best  textile 
dyers  are  almost  unknown  in  the  paper  trade.  The  coloring  of  an 
engine  of  stock  is  usually  only  a  minor  detail  in  the  work  of  a 
busy  superintendent,  although  brightness  and  evenness  of  color 
are  among  the  most  important  factors  in  determining  the  quality 
of  his  product. 

The  term  "  color  "  as  used  in  paper-making  is  applied  much  more 
generally  to  those  nice  distinctions  in  shade,  tint,  and  general 
appearance  which  are  to  be  observed  in  papers  of  the  same  class 
than  to  the  actual  color  of  the  sheet  in  the  ordinary  sense  of  the 
word. 

The  materials  directly  concerned  in  coloring  may  be  roughly 
classified  as  pigments  and  dyes.  Pigments,  of  which  ultramarine 
may  be  taken  as  a  type,  consist  of  fine,  insoluble,  intensely  col- 
ored particles  which  are  distributed  through  the  sheet  in  quantity 
sufficient  to  give  the  desired  tint.  Dyes  must,  from  their  nature, 
be  soluble  until  they  are  fixed  or  developed  upon  the  fibre  either 
by  entering  into  loose  combination  with  the  substance  of  the  fibre 
or  through  the  intermediate  action  of  some  material  called  a  mor- 
dant which  has  an  affinity  for  both  the  fibre  and  the  dye. 

Dyes  which  are  taken  up  by  the  fibre  without  a  mordant  are 
called  substantive  colors,  while  those  which  need  a  mordant  are 
termed  adjective  colors.  The  classification  is  usually  made  with 
reference  to  silk  or  wool,  as  these  fibres  have  much  more  affinity 
for  colors  than  those  of  vegetable  origin. 

The  number  of  pigments  used  by  paper-makers  is  quite  limited, 


COLORING.  321 


and  most  of  these  are  referred  to  in  Chapter  VIII.  under  Mineral 
Colors.  The  pigments  may  either  be  added  directly  to  the  stock 
in  the  engine,  as  in  case  of  ultramarine,  orange  mineral,  and  Vene- 
tian red,  or  they  may  be  formed  upon  the  fibre,  as  when  chrome  yel- 
low is  produced  by  the  addition  of  a  solution  of  bichromate  of 
potash  followed  by  one  of  sugar  of  lead. 

Prussian  blue  was  at  one  time  always  made  at  the  mill  by  mix- 
ing a  solution  of  copperas  with  one  of  yellow  prussiate  of  potash, 
washing  the  precipitated  color  by  decantation  and  oxidizing,  either 
by  exposure  to  the  air  or  by  addition  of  a  solution  of  bleaching- 
powder.  Prussian  blue  is  apt  to  give  a  greenish  tint  to  the  paper, 
and  should  always  be  added  after  the  alum  and  before  the  size,  as 
the  color  is  discharged  by  alkalis. 

The  complex  and  peculiar  pigment  known  as  ultramarine  is 
largely  used  in  paper-making,  and  the  term  is  always  understood 
to  apply  to  the  blue  pigment,  although  red,  green,  yellow,  and 
violet  ultramarines  are  known.  Common  ultramarine  often  has 
a  greenish  cast.  The  color  of  a  sample  of  the  pigment  is  always 
made  darker  by  moisture,  and  for  this  reason  the  low  grades  some- 
times contain  added  water,  glycerine,  or  molasses.  They  are 
lightened  in  color  by  admixture  of  clay,  or  sulphate  of  lime,  or 
sulphate  of  barium. 

Ultramarine  is  very  sensitive  to  acid  and  to  acid  alums,  but  the 
different  samples  vary  considerably  in  their  power  to  withstand 
this  action  without  loss  of  color.  A  little  red  is  commonly  used 
with  the  pigment  to  improve  the  shade.  Owing  to  the  difficulty 
of  thoroughly  wetting  a  dry  powder,  it  is  well  to  mix  the  ultra- 
marine with  a  little  glycerine,  and  to  dilute  with  water  before 
adding  to  the  paper  engine.  Spots  due  to  small  lumps  of  the 
powder  which  break  up  under  the  calender  rolls  are  otherwise 
likely  to  appear. 

The  yellow  pigments  are  chroinate  of  le&d  and  yellow  ochre. 
The  former  is  used  either  as  canary  paste,  or  as  a  powder,  but 
most  commonly  it  is  formed  on  the  fibre  in  the  engine.  For  this 
purpose  a  solution  of  bichromate  of  potash  is  added  to  the  stock, 
and  ten  or  fifteen  .minutes  later  one  of  sugar  of  lead.  The  usual 
proportion  is  one  pound  of  bichromate  to  every  two  pounds  of  the 
lead  salt.  Alums,  whether  basic  or  acid,  have  no  effect  upon 
chrome  yellow,  but  bleach  residues  and  alkalis  give  it  an  orange 
tone,  which  may  with  sufficient  alkali  pass  to  red.  The  pigment 


322  THE  CHEMISTRY  OF  PAPER-MAKING. 

is  much  used  with  blues  to  form  green.     With  Venetian  red'  it 
gives  an  orange. 

Dyes, — Cochineal  as  a  coloring-matter  has  been  used  for  a  very 
long  time  for  tinting  papers  rose  or  scarlet.  The  dye  is  not  so 
durable  as  some  others  of  the  same  nature,  but  is  of  exceptional, 
purity  and  of  rare  brilliance.  It  is  most  frequently  used  along 
with  ultramarine  or  other  blues,  for  whitening  pulp  in  the  produc- 
tion of  high-class  papers.  Since  the  discovery  of  the  coal-tar 
colors  the  use  of  cochineal  has  been  largely  superseded  by  fuch- 
sine,  or  magenta,  or  eosin.  Notwithstanding  this,  there  are  cir- 
eumstajfcceb  under  which  cochineal  is  still  used,  yielding  rose, 
pink,  or  searlet  colors  of  any  depth  of  shade,  and  remarkably 
pleasing  to  the  eye.  Its  cost,  judged  from  the  standpoint  of 
tinctorial  power,  is  greater  than  other  dves  of  the  same  color, 
more  especially  those  belonging  to  the  aniline  series. 

Cochineal,  as  is  we  1  known,  is  the  body  of  an  insect  found  in 
Mexico  and  other  parts  of  Central  America,  and  is  therefore,  per- 
haps, the  only  dye  oi  animal  origin  known  to  dyers.  Although 
it  was  originally  found  in  the  central  part  of  the  American  con- 
tinent, successful  attempts  have  been  made  to  cultivate  its  growth 
in  other  hot  countries  ;  hence  large  consignments -are  sent  to  Eng- 
land and  other  parts  of  Europe,  from  Algeria,  Teneriffe,  Madeira, 
etc.  The  te-male  insects,  which  yield  a  larger  amount  of  coloring- 
matter  than  the  males,  are  carefully  gathered  from  the  cactus 
plant,  upon  which  they  live,  and  are  killed  by  roasting  in  a  stove 
or  by  exposure  on  plates  in  the  sun.  The  dried  flies  are  then 
rubbed,  sieved  to  free  them  from  dirt,  and  finally  sorted.  The 
larger  grained  variety  is  ihe  best.  They  present  a  some  what 
shrivelled  appearance  of  a  dark  brownish  red  color  with  frequent 
patches  ot  a  silvery  lustre. 

The  coloring-matter  contained  in  cochineal  is  called  carminic 
acid.  The  behavior  of  this  carminic  acid  toward  chemical  salts, 
etc.,  shows  the  paper-maker  very  clearly  the  various  reactions 
which  take  place  in  the  beater  engine  under  the  circumstances 
which  usually  prevail  there,  and  therefore  it  is  important  that 
these  reactions  be  -kn6wn,  so  that  he  can  regulate  the  shade  and 
otherwise  produce  in  the  sheet  of  paper  to  be  made,  a  good,  clear 
color  of  uniform  brilliant  appearance.  The  aqueous  extra&t  of 
cochineal  is  a  deep  red  liquid,  which  color  is  transformed  into  a 
deep  violet  on  the  addition  of  lime-water,  while  tine  addition  of 


COLORING.  323 


a  solution  of  acetate  of  lead  causes  a  deep  violet  blue  lake 
to  separate  out  in  the  form  of  a  precipitate.  If  a  solution  of 
alum,  cream  of  tartar,  or  acid  oxalate  of  potash  be  added  to  it,  the 
albuminous  substance  which  is  dissolved  along  with  the 'coloring- 
matter  from  the  flies,  coagulates  and  carries  down  the  canninic 
acid  as  a  flocculent  precipitate  of  a  beautiful  deep  carmine  color. 
This  is  the  purest  and  strongest. carmine.  It  is  of  great  coloring- 
power,  and  in  order  to  weaken  it  for  industrial  purposes,  it  is 
mixed  with  colorless  substances,  such  as  starch. 

When  canninic  acid  is  separated  from  aqueous  decoctions  of 
cochineal  by  means  of  metallic  oxides,  the  compounds  formed  are 
called  carmine  lakes.  Thus,  when  an  alkaline  carbonate  (carbon- 
ate of  soda)  dissolved  in  water  is  added  to  a  decoction  of  cochineal 
which  contains  alum,  a  beautiful  colored  compound  of  the  car- 
minic  acid  and  the  alumina  of  the  alum  separates  out,  which  is 
essentially  a  carmine  lake.  In  the  same  way,  when  "tin  crys- 
tals," previously  dissolved  in  water,  are  added  to  a  slightly  alka- 
line decoction  of  cochineal,  the  oxide  of  tin  combines  with  the 
canninic  acid,  forming,  as  above,  a  beautiful  carmine  lake.  The 
aqueous  extract  of  cochineal  is  unaltered  by  the  addition  of  very 
dilute  acids.  Alkalis,  on  the  other  hand,  change  the  original 
crimson  to  a  bluish  red.  These  reactions  show,  in  a  general  way, 
what  will  take  place  should  any  of  these  chemicals  be  brought 
into  contact  with  the  color  when  in  the  beater.  An  excess  of  free 
alkali  (rosin  size),  for  example,  will  impart  a  bluish  shade  to  the 
pulp. 

There  are  two  decoctions  ®£  cochineal  used  when  tinting  papers 
-with  this  dye;  namely,  the  aqueous  and  ammoniacal  extracts*  The 
formerds  simply  prepared  by  grinding  the  cochineal  flies  to  powder 
in  a  large  mortar  and  gently  boiling  them  in  pure  soft  water  for 
half  an  hour  in  an  ordinary  copper.  The  first  extract  is  then 
•drawn  off,  and  the  boiling  repeated  several  times  with  fresh 
portions  of  water.  The  extracts  are  then  mixed  and  carefully 
filtered  through  a  close  cotton  bag- 

The  ammoniacal  extract  is  prepared  by  adding  a  known  weight 
of  the  pulverized  dye  to  spirits  of  ammonia  in  a  carboy,  with 
constant  stirring,  the  proportions  being  10  Ibs.  of  cochineal  to 
three  gallons  of  atnmonia  liquor  of  66  per  cent.  The  carboy  and 
contents  are  then  close! v  corked  up  and  laid  aside  for  several  days 
in  a  warm  room,  the  temperature  of  which  is  kept  constant  until 


324  THE  CHEMISTRY  OF  PAPER-MAKING. 

the  liquor  has  thickened.  The  longer  it  is  kept,  the  better  its 
quality.  Before  adding  this  extract  to  the  pulp  in  the  heater,  it 
must  be  diluted  with  water  and  carefully  filtered. 

Pulp  which  has  been  mordanted  with  alum  and  covered  with 
cochineal  produces  a  more  durable  tone  than  pulp  not  mordanted 
at  all.  But  the  color  is  somewhat  dull,  and  is  brightened  by  the 
use  of  a  little  oxalic  acid.  This  acid  imparts  a  yellowish  shade  to 
the  crimson,  especially  if  much  of  it  be  used.  The  presence  of  an 
excess  of  alkali  (rosin  size)  changes  the  tone  from  red  to  blue,  and 
therefore  the  size  must  not  be  in  excess.  Indeed,  when  sizing,  the 
alum  or  sulphate  of  alumina  must  be  added  until  the  characteristic 
blue,  produced  by  the  alkali,  has  vanished.  An  addition  of  "  tin 
crystals  "  brightens  the  color  and  develops  its  full  brilliance.  A 
much  better  reagent  to  use  for  the  development  and  "fixing"  of 
cochineal  colors  is  the  mordant  known  in  trade  as  "  scarlet  liquor," 
and  which  is  so  extensively  used  in  the  dyeing  and  calico-printing 
industries.  Scarlet  liquor  is  a  chloride  of  tin  specialty  prepared  in 
the  liquid  form  and  sold  in  carboys.  Its  action  upon  the  pulp  in 
the  beater  is  much  surer  and  quicker  than  utin  crystals,'7  and 
on  this  account  is  to  be  preferred.  A  small  quantity  of  tartaric 
acid  is  used  along  with  it. 

With  the  aqueous  extract  of  cochineal  it  is  somewhat  difficult 
to  obtain  uniform  results,  and  for  this  reason  it  is  better  to  employ 
the  ammoniacal  extract,  which,  in  conjunction  with  alum  and  tar- 
taric acid,  is  the  best  way  of  coloring  paper  pulp  with  this  dye. 
The  alum  and  tartaric  acid  neutralize  the  ammoniacal  cochineal 
and  precipitate  the  carmine  lake  upon  the  pulp  in  a  very  uniform 
state.  The  pulp  for  this  purpose  should  be  well  washed  and  free 
from  bleach  liquor.  The  alum  and  tartaric  acid  are  then  added, 
and  when  thoroughly  incorporated  with  the  fibre  the  ammoniacal 
cochineal  is  poured  in  in  sufficient  quantity  to  produce  the  depth 
of  color  required.  Tin  crystals  slightly  acidified  with  muriatic 
acid  improve  and  brighten  -the  color. 

When  coloring  with  this  dye  the  "  sizing  "  must  be  carried  out 
with  care.  The  pulp  is  usually  colored  before  adding  the  size. 
The  alum  may  then  be  added,  and  when  thoroughly  mixed,  the 
rosin  size,  which  should  be  largely  diluted  with  water,  is  grad- 
ually poured  in.  The  reason  of  this  is  obvious.  If  the  size  be 
added  in  the  strong  and  concentrated  state,  the  precipitated  flakes 
of  rosin  may  surround  portions  of  the  colored  pulp,  changing  them 


COLORING,  325 


to  blue,  which  may  not  be  affected  by  the  acidity  of  the  alum, 
even  though  this  is  in  excess.  For  this  reason  the  pulp  is  kept 
distinctly  acid,  with  alum  or  the  other  mordants  used,  before  run- 
ning it  into  the  stuff  chest. 

Papers  colored  with  cochineal  are  very  easily  bleached  by  chlo- 
rine or  bleach  liquor,  and  are  very  susceptible  to  change  under  the 
influence  of  alkalis  and  acids.  When  heated  in  lime-water  the 
crimson  changes  to  violet.  Dilute  oil  of  vitriol  transforms  it.  into 
orange.  Alcohol  acidified  with  muriatic  acid  changes  the  color 
into  a  dirty  yellow,  while  chloride  of  copper  converts  it  into  brown. 
By  these  tests  cochineal  colors  may  be  known. 

Since  the  discovery,  by  Perkins,  in  1856,  of  mauvein,  the  list  of 
materials  available  for  the  purposes  of  the  dyer  and  paper-stainer 
has  been  enriched  by  a  long  series  of  very  complex  synthetical 
products  derived  from  coal  tar  and  known  collectively  as-  the  coal- 
tar  colors.  These  are  generally  the  salts,  as  the  hydrochloride  or 
acetate,  of  colorless  bases.  For  a  time  they  were  in  some  disre- 
pute because  of  their  want  of  fastness,  but,  as  now  made,  some  of 
them  are  more  fast  than  indigo,  while  their  brilliancy  and  con- 
venience have  enabled  them  to  largely  displace  the  older  coloring- 
materials.  The  two  most  prominent  classes  of  these  dyes  are  those 
derived  from  aniline  and  the  more  recent  azo  dyes,  which  last  form 
a  whole  series  of  fast  and  brilliant  colors,  all  containing  nitrogen. 

As  the  study  of  the  coal-tar  colors  forms  one  of  the  most  difficult 
branches  of  chemistry,  owing  to  their  immense  number  and  great 
complexity  of  composition,  110  attempt  can  be  made  in  the  present 
chapter  to  do  more  than  refer,  under  their  commercial  names,  to  a 
few  of  those  more  commonly  employed  in  paper-making. 

The  more  prominent  red  dyes  are  magenta,  eosin,  the  fast  pinks, 
and  safranine.  These  are  called  "  straight  colors,"  and  many 
shades  are  made  by  their  proper  blending.  They  are  mordanted 
with  alum,  or  some  extract  like  fustic  containing  tannin,  or  they 
may  be  fixed  by  sugar  of  lead.  The  magentas  are  salts  of  rosani- 
line,  the  hydrochloride  being  a  common  form,  and  they  are  also 
known  commercially  as  fuchsine  and  aniline  red.  They  occur  as 
brilliant  green  crystals  having  the  sheen  noticed  on  .the  backs  of 
certain  beetles.  The  blue  shades  are  purest,  and  well-crystallized 
samples  should  be  preferred.  They  sometimes  contain  arsenic  as 
an  impurity.  They  dissolve  readily  in  water  to  a  magnificent 
crimson  solution. 


326  THE  CHEMISTRY   OF  PAPER-MAKING. 

The  eosins  are  a  class  of  dyes  derived  from  fluoresce'iri.  They 
are  soluble  in  water  and  in  alcohol,  the  latter  solution  being  com- 
monly fluorescent.  They  give  a  red  which  in  some  instances 
inclines  to  blue.  They  form  lakes  with  alum. 

Commercial  safranine  is  a  reddish-brown  powder,  which  forms 
with  water  a  red  solution  from  which  the  color  may  be  fixed  by 
tannin  extracts  or  tartar  emetic.  Under  the  head  of  the  safranine 
dyes  are  comprised,  however,  a  class  of  colors  which  range  in  shade 
from  red  to  blue. 

For  the  browns  between  red  and  yellow,  paper  brown  and  Bis- 
marck brown  are  among  the  colors  used,  the  tint  being  thrown 
to  one  side  or  the  other  by  careful  admixture  of  reds  or  yellows. 
These  browns  are  soluble  in  water,  and  are  best  mordanted  by 
means  of  tartar  emetic. 

Auramine  and  naphthol  are  among  the  principal  yellow  dyes. 
The  former  occurs  as  a  sulphur-yellow  powder,  soluble  in  water 
and  alcohol.  It  may  be  fixed  by  tartar  emetic  or  by  tannin. 

The  green  coloring-matters  derived  from  coal  tar  are  especially 
rich  and  numerous.  The  straight- colors,  brilliant  green,  Victoria 
green,  and  malachite  green,  are  those  most  used,  and  all  three  are 
soluble  in  water. 

The  blue  dyes  are  also  numerous,  but  the  three  most  generally 
employed  are  soluble  blue,  paper  blue,  and  cotton  blue.  Special 
shades  are  obtained  in  commercial  anilines  by  the  admixture  of 
two  or  more  of  these.  All  are  fixed  by  alum. 

Methyl  violet  is  the  color  most  lined  for  violet  and  the  reddish 
shades  of  blue.  It  occurs  as  a  greenish  powder  or  in  crystals. 
The  tint  of  the  commercial  samples  is  made  to  range  from  very 
red  to  very  blue.  The  color  is  precipitated  by  yellow  prussiate 
of  potash. 

The  commercial  dyes  which  give  the  intermediate  shades  and 
colors  are  frequently,  as  has  been  already  indicated,  made  by 
mixing  two  or  more  of  the  straight  colors  in  proportion*  deter- 
mined by  careful  experiment,  Such  admixture  tiiay  often  be 
detected  by  allowing  a  drdp  of  the  solution  to  fa.}}  upon  filter 
paper,  when,  as  the  drop  spreads  out,  differently  colored  zones 
appear.  It  is,  in  many  cases,  not  difficult  to  match  such  a  sample 
of  mixed  color  by  making  up  a  solution  containing  a  given  quan- 
tity of  the  sample  for  a  standard,  and  then  mixing  together,  in 
carefully  noted  quantities,  solutions  of  the  other  dyes  which  seem 


COLORING.  827 


<-.<>  be  required,  until  the  standard  solution  has  been  matched. 
Prom  the  strength  and  quantities  of  the  other  solutions  used  may 
then  be  calculated  the  proportions  needed  of  the  different  dyes.  All 
the  solutions  are  best  made  rather  dilute,  and  the  tints  are  most 
easily  compared  in  tubes  such  as  are  used  for  nesslerizing  water. 

The  intense  coloring  power  of  these  dyes  makes  them  especially 
liable  to  adulteration  or  dilution  by  inert  q,nd  valueless  materials. 
Sugar,  dextrine,  common  salt,  and  sulphate  of  soda  are  commonly 
used  for  this  purpose  and  are  for  the  most  part  unobjectionable, 
except  as  they  may  carry  dirt  or  diminish  the  tinctorial  power  of 
the  sample.  The  salt  and  sulphate  of  soda,  Glauber's  salt,  have  a 
certain  value  as  mordants,  but  when  required  they  can  be  bought 
more  cheaply  under  their  common  names.  This  sophistication  has 
been  the  direct  result  of  the  demand  b\r  the  buyers  for  cheap 
colors,  and  it  may  be  taken  as  a  general  rule  that  the  best  colors 
will  be  found  the  cheapest  when  the  cost  is  estimated,  as  it  should 
be,  on  the  ton  of  paper  colored. 

For  use  in  the  paper  engine,  it  is  customary  to  select  Chose  colors 
which  are  soluble  in  water,  as  the  use  of  the  alcohol  colors  involves 
considerable  extra  expense.  The  best  colors  will  stand  boiling; 
those  of  lower  grade  should  be  dissolved  in  hot  water.  The  solu- 
tion, in  either  case,  should  be  carefully  strained  through  flannel 
and  added  to  the  engine  before  the  size  or  alum.  Many  of  the 
color  manufacturers  send  out  special  formulas  for  guidance  in  the 
use  of  their  colors,  and  it  is  well  to  consult  and  follow  these.  When 
the  color  has  been  properly  fixed,  either  by  the  fibre  or  by  the  use 
of  alum  or  other  mordant,  there  should  be  no  tinge  to  the  water 
which  runs  away  when  a  handful  of  the  stuff  is  squeezed.  It  will 
be  commonly  found  that  the  tints  obtained  from  a  givan  color  will 
vary  with  the  furnish,  since  the  different  fibres  take  the  color  dif- 
ferently. Ground  wood  is  especially  -apt  to  change  the  tone  of  a 
color,  but  it  is  in  any  case  impossible  to  lay  down  general  rules 
which  can  replace  experience. 

The  coloring  of  paper  to  the  exact  shade  required  by  the  buyer 
is  somewhat  complicated  by  the  fact  that  .the  color  of  the  stuff  in 
the  beater  is  never  that  of  the  finished  paper,  but  always  darker,, 
mainly  because  of  thy  large  amount  of  water  present,  but  also  in 
some  cases  because  oi  the  effect  which  the  heat  of  the  dryers  has 
upon  certain  delicate  colors.  It  is,  for  this  reason,  often  custom- 
ary for  superintendents  to  reduce  to  pulp  the  sheet  they  wish  to 


328  THE  CHEMISTRY  OF  PAPER-MAKING. 

match,  and  then  to  bring  the  stuff  in  the  engine  to  this  shade.  By 
folding  a  sheet  and  looking  into  it,  as  into  a  partly  opened  book, 
the  intensity  of  a  faint  tint  is  much  increased,  through  multiple 
reflection  of  the  light,  and  in  this  way  a  conclusion  may  often  be 
reached  as  to  the  colors  required  to  match  the  given  shade. 

A  rough  idea  of  what  the  color  of  the  finished  sheet  will  be  may 
be  obtained  by  squeezing  a  handful  of  the  stuff  and  then  beating 
it  out  between  the  hands  and. drying,  but  the  thickness  and  uneven- 
ness  of  the  cake  introduce  a  considerable  chance  for  error.  When 
several  engines  of  a  given  color  have  to  be  made  up,  it  is  a  common 
practice  to  retain  a  bowl  of  the  stuff  from  the  first  engine  and  to 
use  this  as  the  standard  for  comparison.  The  color  of  the  stuff 
in  the  bowl  is,  however,  apt  to  change  on  standing,  and  especially 
to  grow  darker.  The  better  way  is  to  squeeze  out  a  handful  of 
the  stuff  and  match  the  next  engine  by  it,  the  sample  from  the 
second  engine  then  serving  for  the  following  one,  and  so  on. 
Since  it  is  a  difficult  thing  at  best  to  secure  an  exact  match  be- 
tween two  lots  of  paper,  every  care  should  be  taken  to  have  the 
conditions  under  which  comparisons  of  color  are  made  as  nearly 
alike  every  time  as  possible.  The  character  of  the  light  coming 
through  one  window  may  be  so  far  different  from  that  at  another 
one  as  to  cause  appreciable  difference  in  the  tint  of  colors  examined 
at  one  place  or  the  other.  Light  from  the  north  is  best. 

Great  differences  in  light  are  caused  by  reflection  from  the 
objects  outside,  and  it  is  therefore  advisable  to  select  some  one 
place  in  the  mill  where  the  light  is  good,  and  to  do  all  the  match- 
ing there.  At  night  an  arc  light  is  best  for  showing  colors,  but 
wherever  possible  a  change  of  colors  should  only  be  made  in  the 
daytime. 

The  kind  of  filler  used  has  a  considerable  influence  on  the  color 
of  the  sheet,  and  when  changing  onto  a  new  filler  or  modifying  the 
proportions  of  the  old  one  it  often  becomes  necessary  to  change 
the  color  furnish.  The  same  observations  of  course  apply  when  the 
mixture  in  the  engine  is  modified  by  the  addition  of  broken  paper. 

Numerous  color  furnishes  are  given  by  Dunbar,  —  The  Practical 
Paper-Maker,  London,  1887,  —  which  will  be  found  useful  as 
indicating  the  proportions  in  which  the  various  coloring-matters 
are  employed  in  the  production  of  colored  papers.  In  the  use  of 
such  general  recipes,  however,  due  allowance  must  always  be  made 
for  the  character  of  the  stock  and  other  materials  in  the  furnish. 


WATER.  329 


CHAPTER  VII. 

WATER. 

THE  very  large  quantities  of  water  which  are  required  in  the 
processes  of  paper-making,  and  the  readiness  with  which  the  qual- 
ity of  the  product  is  influenced  hy  conditions  which  affect  the 
character  of  the  water-supply,  make  the  subject  one  of  the  first 
importance  to  the  manufacturer.  Water  which  is  pure  in  the 
strict  chemical  sense  —  that  is,  water  which  contains  no  foreign 
substance  —  is  never  obtained  in  nature,  so  that,  from  the  manu- 
facturing as  well  as  from  the  sanitary  standpoint,  we  have  to 
consider  waters  with  reference  to  the  amount  and  character  of 
the  foreign  constituents  which  they  contain,  and  these  include 
not  only  the  mineral  or  inorganic  substances  which  may  he 
present,  but  also  the  various*  minute  forms  of  plant  and  animal 
life. 

Waters  are  broadly  divided  into  surface  and  ground  waters, 
surface  waters  comprising  those  of  brooks,  rivers,  ponds,  and 
lakes,  while  ground  waters,  as  their  name  implies,  are  those  which 
have  percolated  to  some  depth  through  the  soil  and  the  underly- 
ing porous  strata.  Although  all  these  waters  have  a  common 
origin  in  rain,  and  though  surface  waters  become  ground  waters, 
and  the  reverse,  there  are  yet  certain  broad  distinctions  between 
the  classes,  which  are  the  result,  in  the  main,  of  the  action  of  light 
and  air  in  the  one  case,  and  of  the  filtering  and  oxidizing  power  of 
porous  earth,  together  with  the  solvent  action  of  the  water,  in  the 
other.  Surface  waters  are  apt  to  be  more  or  less  highly  colored, 
and  they  contain  plant  and  animal  life,  to  which,  in  fact,  much  of 
their  color  is  often  due.  Ground  waters  are  clear  and  colorless, 
but  they  show  a  greater  content  of  mineral  matter. 

Soft  waters  are  such  as  contain  comparatively  little  of  those 
mineral  constituents  which  have  the  power  of  decomposing  soap, 
while  hard  waters  are  those  in  which  this  power  is  present  in 
a  marked  degree.  Lime  salts  are  the  most  common  cause  of 
hardness  in  water,  and  of  these  the  carbonate  is  most  conspicuous, 


330  THE  CHEMISTRY  OF  PAPER-MAKING. 

although  in  some  localities  hardness  may  be,  due  to  sulphate. 
Common  salt  and  salts  of  magnesium,  when  present,  have  the 
same  effect,  the  latter  to  an  extent  which  is  even  more  marked 
than  in  case  of  those  of  lime.  The  hardness  of  a  water,  as  deter- 
mined by  the  quantity  of  standard  soap  solution  required  to  pro- 
duce a  permanent  lather,  is  expressed  in  degrees,  each  degree 
indicating  a  hardness  equivalent  to  that  due  to  one  grain  of 
carbonate  of  time  in  a  gallon  of  water,  or,  better,  one  part  of 
carbonate  of  lime  to  100,000  parts  of  water. 

For  washing  stock  and  for  boiler  purposes,  a  soft  water  is  desir- 
able, or  even  necessary,  from  its  greater  solvent  power  in  the  one 
case,  and  its  slight  tendency  to  form  scale  in  the  other.  Its 
importance  in  the  other  departments  of  the  manufacture  is  rather 
overestimated;  for  in  boiling  stock,  bleaching,  or  furnishing  ar» 
engine,  the  softest  water  is*  made  hard  by  the  materials  employed 
in  the  operation.  The  use  of  a  very  hard  water  will,  however, 
undoubtedly  increase  the  quantity  of  size  required,  since  the  size 
is  merely  a  soap,  and  the  insoluble  lime  or  magnesia  soaps  thrown 
down  have  little  or  no  sizing  power.  Hardness  due  to  sulphate 
of  lime  will  also  discharge  the  color  of  certain  aniline  blues, 
when  these  are  used  in  the  small  amounts  required  in  white 
papers. 

The  most  important  quality  of  water,  from  the  paper-maker's 
Standpoint,  is  that  of  color.  The  volume  of  water  used  in  making 
a  ton  of  paper  is  so  gr.eat,  —  it  is  probably  never  less  than  50,000, 
and  sometimes  as  much  as  200,000,  gallons,  —  and  the  fibres  form 
so  perfect  a  filter,  besides  possessing  the  power  of  removing  much 
of  the  dissolved  coloiing-inatter,  that  the  presence  in  the  water 
of  even  minute  quantities  of  material  -injurious  to  color  may  render 
impossible  the  manufacture  of  paper  of  high  grade. 

The  purest  natural  waters  are  clear  and  colorless  when  exam- 
ined in  small  quantities,  but  in  the  mass  they  have  a  bluish  tint. 
Surface  waters  show  every  gradation  in  color,  from  this  pellucid 
clearness  through  yellow  and  reddish  tints  to  the  dark  brown  of 
swamp  waters.  The  only  systematic  attempt,  within  our  knowl- 
edge, to  apply  a  standard  to  the  measurement  of  the  depth  of 
color  found  in  waters,  has  been  made  by  Dr.  Drown,  chemist  to 
the  State  Board  of  Health  of  Massachusetts,  in  the  course  of  his 
exhaustive  examination  of  the  water-supplies  of  the  State.  The 
method  adopted  was  that  first  suggested  by  Prof.  Leeds.  In  tht 


WATER.  331 


reports  of  the  Board  the  color  of  the  waters  is  expressed  by  num- 
bers which  increase  with  the  amount  of  color.  Water  having  a 
color  of  1.0  Is  a  decided  yellowish  brown.  This  color  corresponds 
to  that  obtained  by  nesslerizhig  1  c.c.  of  the  standard  ammonium 
chloride  solution  used  in  the  determination  of  the  ammonia  in 
water.  By  this  standard  the  average  depth  of  color  of  the  Con- 
necticut River  water  at  Turner's  Falls,  is  0.30,  though  it  ranges 
from  0.10  to  0.80.  The  Merrimac  River  at  Lawrence  shows  a. 
somewhat  higher  average,  —  0.33,  —  though  no  single  sample  had 
a  color  above  0,70. 

The  color  of  water  is  due  mainly  to  those  substances  which 
leach  out  from  the  ulmic  matter  formed  by  the  decay  of  leaves, 
grasses,  and  similar  material  in  the  soil  or  on  the  surface  of  the 
ground.  In  other  words,  the'  cause  in  most  cases  or  in  greater 
pfcrt  is  decaying  vegetation.  If  this  decay  has  proceeded  far,  as 
in  peaty  swamps,  the  brown  coloration  thus  derived  is  very  per- 
manent in  character. 

The  immense  number  of  microscopic  plants  which  are  developed 
in  some  surface  waters  at  certain  seasons  of  the  year  are  an  impor- 
tant cause  of  color  in  such  waters.  Such  growths  are  most  com- 
mon in  summer*  though  the  periods  of  greatest  abundance  „  are 
Often  not  coincident  in  case  of  the  different  genera.  As  a  rule, 
however,  the  more  important  genera  appear  year  after  year  in 
much  the  same  order,  so  that  where  a  particular  organism  has 
caused  trouble  at  one  time,  a  recurrence  of  the  difficulty  at  about 
the  same  time  may  be  expected  the  following  year,  if  the  condi- 
tions remain  the  same.  The  most  important  of  these  plants*  from 
our  present  point  of  view,  are  the  algse.  These  are  green  op  bluish 
green,  and,  like  the  larger  plants,  derive  their  color  from  chloro- 
phyl  and  require  light  for  their  development.  They  do  not  occur 
to  any  extent  in  rapidly  flowing  streams,  but  thrive  in  ponds  or 
reservoirs  in  which  the  water  is  comparatively  stagnant.  The 
fresh-water  sponges,  which  occur  as  thin  incrustations  upon  objects 
immersed  in  the  water,  or  as  a  coating  within  the  pipes,  are  doubt- 
less, through  their  decomposition,  a  not  infrequent  cause  of  unpleas- 
ant tastes  and  odors  in  water.  They  thrive  best  in  summer  and 
in  water  which  is  in  motion. 

The  suspended  mineral  matter,  clay,  silt,  and  such  material, 
which  a  water  carries  has  at  times  a  marked  effect  upon  the  color 
of  the  water.  This  factor  is  a  very  variable  one,  and  exerts  its 


332  THE  CHEMISTRY  OF  PAPER-MAKING. 

greatest  influence  after  heavy  rains,  which  wash  the  finely  divided 
soil  and  earth  into  the  streams.  The  soluble  mineral  constituents 
have,  for  the  most  part,  no  effect  upon  color.  Even  thxj  soluble 
salts  of  iron  are  rarely  or  never  present  in  amount  sufficient  -to 
perceptibly  color  the  water  while  they  are  present  as  such.  It  is 
when  from  any  cause  the  iron  is  precipitated  as  hydrate  thrft  it  hey 
cause  trouble. 

We  have  occasionally  noticed,  in  case  of  mills  using  unfiitered 
water  drawn  from  ponds,  a  gradual  accumulation  of  a  rust-like 
deposit  in  the  water  pipes,  which  sometimes  was  sufficient  to 
nearly  choke  them  up.  It  is  probable  that  this  difficulty  is  due 
to  the  microscopical  plants  known  as  iron  bacteria,  of  which  the 
commonest  and  most  important  is  Orenothrix  KilJinitma^  or  "  well- 
thread."  Although  perhaps  the  largest  among  the  bacteria,  it  is 
of  course  exceedingly  minute,  and  quite  invisible  to  the  naked  eye, 
until,  by  the  accumulation  of  multitudes  of  cells,  flocks  or  masses 
of  visible  size  are  formed.  The  cells  are  mainly  -cylindrical,  and 
are  united  end  to  end  to  form  threads  or  filaments.  The  presence 
of  salts  of  iron  in  solution  is  necessary  for  their  vigorous  growth, 
and  they  have  the  curious  power  of  -withdrawing  this  iron  from 
the  water  and  depositing  it  in  the  form  of  ferric  oxide  as  a  sheath 
or  tube  around  the  filament.  The  color  of  this  sheath,  which  at 
first  is  hardly  noticeable,  passes  through  this  accumulation  of  iron 
from  pale  yellow  to  deep  brown,  and  there  is  at  the  same  time  a 
gradual  thickening  of  the  wall.  The  thick  and  hard  .sheath  then 
se.em»  no  longer  suited  to  the  activities  Bf  tlie  plant,  and  is 
abandoned  by  the  cells,  which,  as  they  work  out  from  it,  cause 
it  to  take  on  an  increase  of  length  or  a  structure  which  suggests 
branching. 

Orenothrix  has  at  several  times  been  the  cause  of  serious  double 
in  the  water-supplies  of  European  cities,  notably  at  Berlin  in  1878, 
and  at  Rotterdam  in  1887.  Its  occurrence  in  this  country  is  Well 
established,  and  it  is  known  to  be  common  in  Massachusetts.  It 
may  be  removed  and  kept  out  of  a  water  by  thorough  nitration, 
but  may  grow  rapidly  in  an  imperfectly  filtered  effluent.  Light 
is  not  necessarj'  for  its  growth,  and  in  fact  it  thrives  best  in  dark 
reservoirs  or  galleries  arid  in  systems  of  pipe. 

All  waters  consume  small  quantities-  of  bleaching-powder,  the 
amount  in  each  case  depending  upon  that  of  the  organic  matter 
present  in  the  water.  Except  in  rare  cases,  the  loss  of  bleach  thus 


WATER.  338 


occasioned  is  inappreciable,  as   appears  from   our  results   given 
below :  — 

Vwlatile  and  inorganic  Bleaching-powder  (86  per 

matter  iu  water.  cent.)  consumed. 

0.93  grains  per  gallon.  1.77  grains  per  gallon. 

0.35  1.16 

1.167  3.87 

The  mineral  constituents  of  a  water  affect  its  value  for  paper- 
making  mainly  as  they  bear  upon  the  suitability  of  the  water  for 
boiler  purposes.  As  already  pointed  out,  a  soft  water  is  desirable 
for  some  of  the  operations  of  the  mill,  but  its  use  in  a  boiler  is 
almost  essential  if  trouble  from  scale  is  to  be  avoided.  Accord- 
ing to  Haswell,  a  coating  of  scale  one-sixteenth  of  an  inch  ki. 
thickness  causes  a  loss  of  fuel  equal  to  14.7  per  cent.,  while  we 
have  seen  samples  of  scale  an  inch  and  a  quarter  thick.  When 
any  considerable  thickness  of  scale  is  present,  there  is  much  danger 
of  overheating  the  boiler  locally.  This  is  often  followed  by  blis- 
tering or  cracking  of  the  plates  or  collapsing  of  the  tubes,  and 
may  even  cause  explosion,  due  to  the  breaking  of  the  scale  and 
the  sudden  contact  of  the  water  with  the  overheated  plate  below. 

Carbonate  of  lime  is  the  most  frequent  cause  of  boiler  scale. 
It  is  normally  very  slightly  soluble  in  water;  but  if  the  water 
contains  dissolved  carbonic  acid,  the  lime  may  be  brought  into 
solution  as  bicarbonate  in  very  considerable  amount.  The  bi- 
carbonate is  the  cause  of  what  is  called  temporary  hardness,  for 
upon  boiling  it  is  decomposed,  with  precipitation  of  the  carbonate. 
According  to  Couste*,  this  precipitation  is  complete  at  200°  F.,  or 
under  the  conditions  which  obtain  in  most  boilers.  Carbonate  of 
magnesia,  which  is  similarly  soluble  in  the  presence  of  dissolved 
carbonic  acid,  and  similarly  precipitated  on  boiling,  is  also  likely 
to  form  scale.  Chloride  of  magnesia,  although  extremely  soluble 
in  "water,  is  nevertheless  objectionable,  because  at  high  pressures 
it  is  decomposed,  with  liberation  of  hydrochloric  acid  and  forma- 
tion of  hydrate  of  magnesia,  the  latter  acting  as  a  sort  of  cement 
in  binding  together  other  scale-forming  materials-.  The  precipi- 
tated carbonate  of  magnesia  undergoes  a  like  decomposition, 
carbonic  acid  being  set  free. 

The  general  character  of  a  carbonate  scale  appears  from  the 
following  analysis,  but  the  proportions  show  considerable  varia- 
tion in  different  samples* 


334  THE  CHEMISTRY  OF  PAPER-MAKING. 

ANALYSIS  OF  A  CARBONATE  SCALE. 

(Silvester.) 

Per  cent. 

Carbonate  of  lime     .     . .75.85 

Sulphate  of  lime  ...........    3.08 

Hydrate  of  magnesia 2.56 

Chloride  of  sodium. 0.45 

Silica      ..............     7.66 

Oxides  of  iron  and  alumina .     2.96 

Organic  matter     .     .    ,     .     .     .     ....     .     .     3.04 

Moisture 3.20 

100.00 

Sulphate  of  lime*  although  rather  soluble  in  water,  has  its  point 
of  greatest  solubility  at  95*  F.,  and  from  a  solution  saturated  at 
this  temperature,  the  salt  is  therefore  gradually  thrown  out  as  thfej 
temperature  rises.  Moreover,,  the  hydrated  sulphate,  CaSO4  2:  H20, 
begins  to  lose  its  water  of  crystallization  at  about  260°  F.,  and  is 
converted  into  the  anhydrous  sulphate,  CaSO4 ,  which  is.  far  more 
insoluble.  Both  these  actions  combine  to  produce  a  hard  scale  as 
the  sulphate  accumulates  in  the  boiler,  and  the  usual  methods  of 
softening  water  are  of  comparatively  little  value  when  sulphate 
of  lime  is  present. 

Much  silica  is  troublesome  in  a  water  used  for  boiler  purposes, 
as,  when  deposited,  it  serves  as  a  binding  material  and  causes  the 
production  of  a  very  hard  scale. 

Acid  waters  are  rarely  met  with  in.  this  country,  where  there  is 
comparatively  little  contamination  of  streams  by  manufacturing 
waste ;  but  in  sulphite  mills  there  is  danger,  if  for  any  reason 
cheek-valves  do  not  work  properly,  that  some  of  the  liquor  from 
the  digesters  may  find  its  way  into  the  generating  boilers--  and 
cause  corrosion,  which  is  more  to  be  dreaded  than  scale.  Cylinder 
oils  not  infrequently  contain  free  fatty  acids,  and  when  these  are 
present,  they  pass  with  the  feed  water  back  into  the  boiler  and 
corrode  the  metal.  Very  alkaline  waters  also  are  apt  to  attack 
the  poiler  fittings  and  cause  leakage. 

A  100-horse-power  boiler  evaporates  30,000  Ibs.  of  water  in  10 
hours,  or  900  tons  in  25  days  of  continuous  working.  Since  the 
mineral  matters  remain  behind  in  the  boiler  as  the  evaporation 
of  the  water  proeeeds,  it  becomes  obvious  that  apparently  iusig- 


WATER.  335 


uificant  amounts  of  mineral  impurity  may,  in  this  process  of 
concentration,  accumulate  to  such  an  extent  as  to  cause  serious 
inconvenience  from  mud  and  scale.  A  deposit  of  scale  ^  of  an 
inch  in  thickness  has  already  been  said  to  cause  a  loss  of  fuel  of 
14.7  per  cent.,  while  if  the  scale  is  J-inch  thick,  the  loss  is  said  to 
amount  to  38  per  cent.  A  great  many  materials  have  been  pro- 
posed for  use  in  boilers  as  preventives  of  scale,  but  most  of  them 
are  of  doubtful  value.  Organic  substances  containing  tanriic  acid, 
as.  for  instance,  oak  or  hemlock  bark,  ara  sometimes  used,  their 
value  depending  on  the  tannic  acid.  Other  materials,  which  either 
contain  acetic  acid,  or  which  are  of  such  a  nature  that  the  acid 
maybe  developed  from  them  under  the  heat  and  pressure  of  the 
boiler,  have  also  been  used  with  some  success,  but  are  objectionable, 
from  the  danger  that  the  acid  due  to  them  may  corrode  the  boiler. 
Crude  or  refined  petroleum  has  been  recommended  for  use  with 
waters  containing  large  amounts  of;  sulphate  of  lime.  The  refined 
oil  is  preferable,  as  the  residuum  from  the  crude  oil  is  apt  to  cake 
on.  the  plates  and  bind  the  scale  more  firmly.  Abroad,  sulphate 
waters  are  purified  by  the  addition  of  carefully  regulated  amounts 
of  either  caustic  soda  or  soda-ash,  or,  more  rarely,  .barium  chloride. 
Both  the  caustic  soda  and  soda-asli  result  in  precipitation  of  car- 
bonate of  lime,  but  the  soda  ash  is  to  be  preferred.  The  barium 
<  hloride  forms  the  very  soluble  chloride  of  calcium  and  the  insolu- 
ble sulphate  of  barium.  If  the  alkalis  are  used,  much  care  is 
necessary  to  secure  the  proper  amount,  as  an  excess  causes 
foaming. 

The  method  for  softening  waters  which  is  most  generally  used 
is  that  which  is  especially  applicable  to  waters  containing  lime  or 
magnesia  as  bicarbonates,  and  which  is  due  to  Dr.  Clark.  The 
Clark  process  depends  upon  the  fact  that  when  Ume  is  added  to 
such  waters  the  extra  equivalent  of  carbonic  acid  is  neutralized, 
with  the  result  that  the  lime  originally  present  in  the  water, 
together  with  the  added  lime,  is  thrown  down  as  the  insoluble 
neutral  carbonate,  while  the  bicarbonate  of  magnesia  is  afc  the 
same  time  decomposed,  with  precipitation  of  the  magnesia  as 
hydroxide.  Various  modirications  «f  the  Clark  process  have 
appeared,  which  base  their  claims  to  improvement  upon  .changes 
in  the  apparatus  employed.  The  process  is  perhaps  now  most 
commonly  worked  under  the  form  known  as  the  Porter-Clark 
process,  the  apparatus  for  which -is  .-shown  in  Fig.  72. 


THE  CHEMISTRY  OF  PAPEH-MAKIXG. 


The  tank  shown  at  the  left  of  the  figure  is  fitted  with  a  mechan- 
ical agitator,  and  is  used  for  preparing  the  lime-water  by  admix- 
ture of  water  and  milk  of  lime,  the  latter  being  introduced  through 
the  funnel.  The  lime-water  in  a  carefully  regulated  stream  then 
flows  over  into  the  second  tank,  where  it  meets  the  water  to  be 
purified.  The  outflow  from  this  tank  is  so  controlled  as  to  allow 
sufficient  time  for  the  completion  of  the  desired  reaction,  and  is 


Fi«.  72.  —  THE  PORTER-CLARK  PROCESS. 

finally  sent  through  a  filter-pump,  which  retains  the  precipitated 
material  and  discharges  the  softened  and  clarified  water. 

Filtration.  —  The  purification  of  water  by  filtration  is  a  much 
more  complex  series  of  actions  than  a  mere  mechanical  straining, 
though  this  is  the  most  noticeable,  and  from  our  present  point  of 
view  the  most  important,  office  of  filtration.  In  the  slow  passage 
of  water  through  a  filtering  medium,  the  principle  of  subsidence 
comes  in  play  to  hold  back  particles  so  fine  that  they  would  other- 
wise pass  the  interstices  of  the  filter,  and  the  water  is  at  the  same 
time  subjected  to  influences  which  set  up  changes  of  both  the 
chemical  and  biological  order. 


WATER.  337 


The  primary  action,  of  a  filter  is,  then,  a  straining  one,  to  remove 
the  coarser  particles  of  suspended  mineral  and  vegetable  matter  in 
the  water.  It  is  obvious,  in  addition,  that  if  the  water  were  stand- 
ing in  a  tank,  it  would  gradually  clear  itself  of  these  impurities  by 
the  settling  due  to  gravity.  The  length  of  time  thus  required 
would  depend,  other  things  being  equal,  upon  the  depth  of  water 
in  the  tank.  If  now  the  tank  were  divided  by  a  midway  horizontal 
partition,  or  false  bottom,  the  average  distance  which  each  sus- 
pended particle  must  fall  in  order  to  find  a  resting-place  is  halved, 
and  the  time  needed  for  the  action  similarly  lessened.  Within  a 
filtering  medium  the  number  of  shelves  or  surfaces  upon  which 
the  finest  particles  may  find  lodgment  as  they  settle  is  immensely 
great,  and  it  is  in  large  part  to  this  fact  that  the  efficiency  of  the 
medium  is  due. 

The  action  of  porous  earth,  when  the  passage  of  water  through 
it  is  intermittent,  is  an  oxidizing  one  of  high  order,  from  the  fact 
that  the  water  and  the  gas  are  brought  so  intimately  into  contact. 
In  the  natural  filtration  to  which  surface  waters  are  subjected 
during  their  transformation  into  ground  waters,  this  action  may 
proceed  so  far  under  favorable  conditions  as  to  completely  oxidize 
all  the  organic  matter  originally  present.  In  this  way  not  only  is 
the  suspended  organic  matter  removed,  together  with  the  silt,  by 
the  process  of  straining,  but  the  dissolved  organic  matter  to  which 
much  of  the  color  may  have  been  due  is  consumed  by  oxidation, 
leaving  the  water,  as  in  case  of  all  perfectly  filtered  waters,  entirely 
clear  and  colorless.  The  same  process  goes  on  to  a  considerable 
extent  in  artificial  filtration,  where  the  flow  of  water  is  intermittent 
arid  properly  controlled.  In  continuous  filtration  there  is  little  or 
no  oxidation  of  organic  matter,  and  other  means  are  used  to  secure 
its  removal. 

The  filtration  of  water  has  been  mainly  studied  scientifically 
with  reference  to  its  sanitary  aspect,  and  from  this  point  of  view 
the  removal  of  bacteria  and  other  organisms  is  the  matter  of  first 
importance.  It  has  been  found  that  a  layer  of  fine  sand  one  inch 
in  depth  is  sufficient  to  remove  all  algae  and  animals  from  a  water 
as  rich  in  organisms  as  the  Cochituate  water  of  Boston. 

In  Europe  open  filter-beds  are  very  generally  used  for  the  puri- 
fication of  water  by  filtration,  and  where  the  purification  is  for 
municipal  purposes,  the  beds  are  sometimes  of  enormous  extent. 
The  filter-beds  of  the  various  London  water  companies  cover  an 


838  THE  CHEMISTRY  OF  PAPER-MAKING. 


area  of  more  than  100  acres.  The  continental  cities  have  exten- 
sive and  similar  plants.  The  beds  are  built  up  of  stones  which" 
decrease  in  size  toward  the  top  of  the  bed,  and  which  are  covered 
with  a  layer  of  fine  sand,  generally  two  inches  in  thickness.  The 
average  capacity  of  such  filter  beds  is  found  to  be  1,000,000  gallons 
per  acre  per  twenty-four  hours.  Under  these  con  tions  there  is 
formed  upon  the  surface  of  the  filter-bed  a  growth  of  bacteria 
which  is  called  the  bacteria  jelly,  and  which  prevents  almost  en- 
tirely the  passage  of  bacteria  through  the  filter,  while  of  course  at 
the  same  time  holding  back  the  suspended  impurities  in  the  water. 
The  water  of  the  Spree  contains,  for  instance,  under  normal  condi- 
tions, about  100-,000  bacteria  per  cubic  centimetre,  while  after  pass- 
ing through  the  filter-bed  it  has  only  30-40  per  cubic  centimetre 
when  the  rate  of  flow  is  1,000,000  gallons,  and  only  4-5  when  the 
rate  falls  to  300,000  gallons  per  day. 

The  economic  and  climatic  conditions  which  prevail  in  this 
country  almost  entirely  preclude  the  operation  of  such  extensive 
plants  of  relatively  small  capacity,  so  that  most  municipalities 
and  factories  requiring  filtered  water  make  use  of  some  form  of 
mechanical  filter.  These  may  be  grouped  under  two  systems,  — 
gravity  filters  and  pressure  filters, — and  we  shall  limit  ourselves 
to  the  description  of  representative  types  of  each  system. 

The  efficiency  of  filters  working  under  either  of  these  systems 
is  increased,  and  a  partial  chemical,  a&  well  as  a  complete  mechani- 
cal, purification  of  the  water  effected  by  the  introduction  with  the 
water  of  small  quantities  of  alum  or  other  coagulant.  A  crude 
sulphate  of  alumina  is  generally  employed,  and  seems  to  give  better 
results  than  crystallized  alum.  The  alumina  precipitated  by  the 
action  of  the  alkaline  water  not  only  gathers  the  finely  suspended 
material  into  flocks  of  appreciable  size,  but  also  removes  the  dis- 
solved organic  coloring-matter,  and  forms  a  film  over  the  surface 
of  the  filter,  which  acts,  as  does  the  bacteria  jelly  before  mentioned, 
in  holding  back  minute  organisms.  The  quantity  of  ahim  thus 
used  varies  from  J- grain  to  2  or  3  grains  per  gallon,  the  usual 
maximum  being  2  grains.  If  very  large  amounts  of  loam  are 
present,  in  the  water,  small  quantities  of  lime  may  sometimes  be 
used  first,  and  then  alum. 

The  form  of  gravity  filter  which  has  been  most  generally  intro- 
troduced  is  the  Warren  filter,  shown  in  Figs.  73  and  .74.  A 
Warren  filter-plant  usually  consists  of  a  settling-basin;  one  or 


WATER. 


339 


more  .fillers,  and  a  weir  for  controlling  the  head,  together  with 
the  necessary  pipe  connections.  Each  filter  contains  a  bed  of  fine, 
sharp  sand,  (7,  .two  feet  in  depth,  supported  by  a  perforated  copper 
bottom,  B,  and  for  cleaning  this  bed  an  agitator,  D,  is  provided. 
This  consists  of  a  heavy  rake  containing  13  teeth  25  inches  long, 
rotated  by  a  system  of  gearing,  jfiT,  and  capable  of  being  driven 
into  the  bed  by  means  of  suitable  screw  mechanism,  LM>  whereby 
the  entire  bed  is  thoroughly  scoured. 

The  process  of  filtration  is  as  follows :   The  water  entere  th.o 
settlirig-basjn  through  a  valve  operated  by  a  float,  by  which  a 


FIG,  73. — THE  WARREN  FILTER. — IN  OPERATION. 


constant  level  is  maintained  in  the  entire  filter-system.  The 
water  entering  through  this  valve  passes  through  an  8-bladed 
propeller  of  brass,  from  10  to  16  inches  in  diameter,  so  arranged 
as  to  revolve  freely  with  the  passage  of  the  water.  This,  by  means 
of  two  small  bevel  gears  and  an  upright  shaft,  operates  an  alum 
pump,  consisting  of  six  hollow  arms  radiating  from  a  chambered 
hub  and  bent  in  the  direction  of  rotation.  This  pump  revolves  in 
a  small  tank  containing  a  dilute  standard  solution  of  sulphate  of 
alumina,  or  other  coagulant,  and  by  its  revolution  each  arm  takes 


340 


THE  CHEMISTRY  OF  PAPER-MAKING. 


up  its  modicum  of  alum  water,  passes  it  into  the  hub  and  to  the 
deflector,  which  sends  it  down  to  the  incoming  water. 

When  the  bed  of  a  filter  becomes  clogged,  and  it  seems  best  to 
clean  it,  the  inlet  and  outlet  valves  EF  are  closed,  and  the  wash- 
out Q-  opened,  allowing  the  contents  of  the  tanks  to  escape  to 
the  sewer.  The  agitator  D  is  then  set  in  motion  by  means  of  the 
friction  clutch  with  which  it  is  equipped ;  and  as  the  teeth  on  the 
rake  begin  to  plough  up  the  surface  of  the  bed,  a  slight  amount 
of  filtered  water  is  allowed  to  flow  back  up  through  the  bed,  in 


FIG.  74.  —  THE  WARREN  FILTER.  —  DURING 


order  to  rinse  off  the  dirt  loosened  by  the  scouring  action  of  the 
rake.  This  is  kept  up  until  the  rake  penetrates  to  the  bottom  of 
the  bed,  and  thoroughly  agitates  every  particle  of  material  therein. 
As  soon  as  the  water  flowing  to  the  sewer  appears  to  be  clear,  the 
motion  of  the  rake  is  reversed,  and  it  is  slowly  withdrawn  from 
the  bed.  When  the  teeth  are  raised  above  the  bed,  the  waste  pipe 
is  closed,  the  inlet  valve  J7  opened,  and  the  filter-tank  allowed  to 
fill.  After  waiting  a  few  minutes  for  the  tank  to  resume  its  nor- 
mal condition,  the  outlet  valve  F  is  slowly  opened,  and  filtration 
is  resumed. 


WATER.  341 


The  incoming  water,  having  received  its  proportionate  amount 
of  coagulant,  is  then  allowed  to  remain  in  the  settling-basin  from 
thirty  to  forty  minutes,  to  enable  the  chemical  reaction  between 
the  coagulant  and  the  bases  in  the  water  to  take  place,  and  to 
permit  of  the  heavier  sediment,  together  with  a  portion  of  the 
coagulated  matter,  to  settle  by  subsidence  to  the  bottom  of  the 
tank,  where  it  can  be  drawn  off  at  intervals  into  the  sewer. 

The  partially  purified  water  then  passes  on  through  suitable 
piping  and  valves  to  the  filter,  and,  tilling  the  tank,  passes  down 
through  the  fine  sand  bed,  leaving  all  the  coagulated  matter  upon 
it.  The  filtered  water  makes  its  exit  through  the  main  J. 

The  main,  collecting  the  filtered  water  from  the  various  filters, 
passes  along  between  them  to  the  head-box,  or  weir,  over  which 
the  water  is  compelled  to  pass,  and  which  controls  the  operation 
of  the  filters.  The  top  of  this  weir  is  20  inches  below  the  water 
level  maintained  in  the  filter-system,  and  this  head  of  20  inches 
(equivalent  to  a  pressure  of  three-fourths  of  a  pound  to  a  square 
inch)  is  the  extreme  press-mre  that  can  be  brought  to  bear  upon 
the  filters,  and  it  is  claimed  4hat  they  can  at  no  time  be  pushed 
beyond  the  rate  which  experience  has  shown  to  yield  the  best 
results. 

Two  sizes  of  the  Warren  filter  are  built,  both  being  8  feet  high. 
The  smaller  filter  is  8  feet  8  inches  in  diameter,  and  has  a  capacity 
under  alum  of  200,000-250,000  gallons  per  twenty-four  hours  on 
a  net  area  of  56  square  feet.  Tne  large  size  is  10  feet  6  inches  in 
diameter,  its  net  area  being  84  square  feet,  and  its  capacity  800,000- 
375.000  gallons.  About  5  horse-power  is  required  for  each  agita- 
tor ;  but  as  only  one  filter  is  washed  at  a  time,  the  quantity  of 
power  required  is  irrespective  of  the  size  of  the  plant.  The  filters 
are  usually  washed  every  twelve  hours. 

The  especial  points  of  merit  claimed  for  this  system  are,  first, 
its  cheapness,  and,  second,  the  thorough  and  rapid  cleansing  of  the 
bed  by  the  attrition  of  its  pattielos  set  up  by  the  mechanical  stir- 
ring and  scraping  action  of  tfee  rake. 

The  forms  of  pressure  filter  shown  in  Figs.  75  and  76,  and  built 
by  the  New  York  Filter  Company ,  embody  the  best  features  of  the 
numerous  systems  which,  after  being  developed  on  somewhat 
divergent  lines,  have  now  been  brought  under  the  single  control 
of  this  compaay.  The  filter  shown  in  Fig.  75  consists  of  a  cylin- 
drical steel  shell  built  to  withstand  any  desired  pressure.  The 


342  THE  CHEMISTRY  OF  PAPER-MAKING. 

water  is  introduced  along  a  conduit  running  the  entire  length  of 
the  filter  just  beneath  the  crown.  It  filters  through  4  feet  of  coke 
and  sand,  and  passes  out  by  the  cone  valves  shown  at  the  bottom. 
These  valves  are  imbedded  permanently  in  a  cement  floor  and 
Hush  with  it.  They  are  filled  with  screened  quartz  gravel  to 
prevent  the  passage  of  the  filtering  medium  into  the  mains. 

The  method  ot  cleansing  the  filter  adopted  by  this  company  is 
that  known  as  sectional  washing,  by  which  the  entire  force  of  the 
reversed  current  used  in  washing  is  directed  against  one-third  of 
the  bed  only  for  about  five  minutes ;  it  is  then  shut  off,  and  the 
central  third  of  the  bed  is  scoured  in  the  same  manner;  last,  the 
remaining  third  is  washed.  No  partitions  are  necessary  to  divide 
the  bed,  as  the  current  is  forced  up  nearly  in  a  straight  line.  By 


FIG,  75.  —  SECTIOXAL  WASHING  PRESSURE  FILTER. — NEW  YORK 
FILTER  COMPANY. 

thus  concentrating  the  force  of  the  upward  current  against  a  small 
portion  of  the  bed,  thorough  attrition  and  scouring  of  the  particles 
composing  the  bed  is  accomplished,  while  the  upward  current 
carries  away  the  separated  impurities.  The  capacity  of  such  a 
filter  8  feet  in  diameter  and  20  feet  long  is  about  500,000  gallons 
per  twenty-four  hours;  or,  in  other  words,  two  such  filters  have 
the  capacity  of  a  European  filter-bed  one  acre  in  extent,  when  the 
latter  is  worked  at  the  rate  recommended  by  the  Berlin  authorities. 
Fig.  76  shows  a  vertical  washing-filter  of  essentially  the  same 
type.  These  are  built  in  sizes  ranging  from  12  inches  to  10  feet 
in  diameter,  and  have  a  maximum  capacity  per  twenty-four  hours 
from  about  40*00  to  360,000  gallons.  The  filter  consists  of  a  verti- 
cal steel  shell,  the  cone  valves  at  the  bottom  being  set  on  rubble 
groiiting  and  imbedded  in  cement.  The  space  above  is  about  two- 


WATER.  348 


thirds  filled  with  fine  quartz  silnd  and  coke.  The  water  to  be 
purified  is  admitted  under  pressure  to  the  filter  at  J.,  which 
delivers  the  water  at  the  crown  of  the  filter.  It  then*  passes  down 
through  the  bed  and  out  through  the  cone  valves  to  the  outlet  B, 
leading  to  the  service  pipe.  As  often  as  maybe  necessary,  usually 
ouce  a  day,  the  water  is  shut  off  from  the  inlet  and  allowed  to 
enter  the  filter  in  the  upward  direction  through  the  lower  valves. 
These  are  so  arranged  as  to  admit  the  water  to  the  cones  under- 


FIG.  76. —  SECTIONAL  WASHING  PRESSURE  FILTER. — NEW  YOBK 
FILTER  COMPANY. 

lying  one-third  of  the  bed  at  a  time,  and  the  waste  water,  .carrying 
with  it  the  impurities*  passes  to  the  sewer  through  K. 

A  minute  quantity  of  alum  solution  is  injected  into  the  water 
passing  to  these  filters,  as  in  case  of  practically  all  systems  of  fil-. 
tration  in  use  in  this  country..  In  the  present  instance  a  special 
alum  pump  is  employed  which  delivers  a  positive  quantity  of  the 
solution,  which  is  carefully  regulated  to  suit  the  requirements  of 
the  water. 

A  novel  form  of  plant  is  the  Dervaux  automatic  water-purify- 
ing apparatus,  shown  in  Fig.  77,  for  which  we  are  indebted  to  the 
Papier  Zeitunp.  The  action  of  the  apparatus  is  a  double  one,  cor- 


344 


THE  CHEMISTRY  OF  PAPER-MAKING. 


llcrcinigles 


FIG.  77.  —  DJEKVAUX 

EXPLANATION  OF  TEEMS. 


Wasserzufluss  =  Water  inlet. 

Gereinifftes  Wasser  «  Purified  water. 
Kalkcinschttttung    =  Inlot  for  lijme. 


Kalksattiger       =  T.tme-eaturator. 
Soda  =«  Carbonate  of  six!  a. 

Schlammabflus*  =>  Outlet  for  mechanical  impurities. 


WATER.  345 


responding  to  the  double  nature  of  the  impurities  present  in  the 
water ;  that  is,  it  not  only  acts  to  precipitate  the  dissolved  impuri- 
ties, but  also  to  separate  such  impurities  as  are  in  suspension. 
These  last  are  caught  and  held  in  the  tower-shaped  holder  B~ 
The  water  enters  from  above,  down  through  E>  and  is  made  to 
rise  through  a  series  of  funnels  or  inclined  funnel-shaped  walls. 
On  these  walls  the  coarsest  particles  are  caught,  and  from  them 
they  flow  down  to  the  bottom  of  the  tower,  where  they  collect 
together;  the  water  then  passes  upwards  through  the  filters  JP, 
which  are  made  of  wood  shavings,  and  flows  off,  freed  from  its 
mechanical  impurities,  through  the  opening  T.  In  the  mean  time, 
by  the  addition  of  lime  and  soda,  the  water  has  been  chemically 
purified  in  the  following  way :  — 

The  water  first  flows  in  the  reservoir  (7,  through  the  pipe  H* 
In  C  there  is  a  float  for  regulating  the  flow  of  water.  By  the 
arrangement  of  the  apparatus,  a  part  of  the  water  goes  into  J£, 
through  the  pipe  P,  while  the  rest  passes  through  the  valve  V 
into  the  lime-saturator  8\  S  is  filled  with  lime ;  the  water  first 
meets  the  lime  at  the  bottom  of  the  saturator  and  passes  up 
through  it;  the  conical  shape  of  S  causes  the  rise  to  be  slower 
and  slower  as  the  water  nears  the  top,  so  that  the  milk  of  lime 
at  first  formed  has  plenty  of  time  to  clarify  itself.  The  lime-water 
usually  contains  some  carbonate  of  lirne  in  suspension ;  and  as  this 
is  worthless  for  purpose  of  purification,  it  is  eliminated  by  causing 
the  water  to  flow  over  into  the  cone  _fiT,  which  is  closed  at  the 
bottom.  In  this  cone  the  carbonate  settles  out,  and  may  be  drawn 
off  through  G-. 

The  clear,  saturated  limer water,  containing  1.3  grammes  of  lime 
to  the  litre,  runs  then  directly  into  the  mixing-tube  E.  A  solution 
of  soda-ash  is  made  up  of  a  strength  always  exactly  the  same*  by 
taking  a  known  weight  of  ash,  which  is  placed  in  the  cage  Z,  after 
which  the  tank' Jft  is  filled  to  a  definite  mark  with  water.  This 
solution  slowly  passes  through  the  tube,  provided  with  strainers : 
a  float  in  the  tube  keeps  the  water  in  B  at  a  constant  level.  The 
siphon  N)  one  end  of  which  dips  to  the  bottom  of  jB,  allows  the 
alkaline  solution  to  flow  into  B.  The  regulation  of  the  flow  in  J2 
is  done  as  follows :  — 

The  siphon  Ni&  joined  by  a  chain,  Q,  to  the  float  in  (7.  In  case 
the  flow  of  water  through  Hto  G  is  cut  off,  the  float  sinks,  raising 
-ZVand  thus  stopping  the  flow  of  the  solution.  At  the  same  time 


346  THE 'CHEMISTRY  OF  PAPER-MAKING. 

the  level  in  C  sinks  so  low  that  the  flow  of  water  through  P  and 
F"  ceases ;  as  soon  as  the  flow  of  water  through  H  recommences, 
the  apparatus  is  again  set  in  operation  automatically. 

The  whole  apparatus  comes  to  a  standstill  as  soon  as  the  draw- 
ing off  of  the  pure  water  at  Estops;  this  is  effected  by  a  float  in 
J)  not  shown. 

The  chemical  reaction  going  on  in  the  apparatus  was  roughly 
this :  — 

The  addition  of  the  lime  softens  the  water  by  precipitating  any 
bicarbonate  which  may  be  present,  and  the  excess  of  lime  is 
thrown  down  by  the  carbonate  of  soda.  This,  by  its  precipitation, 
coagulates  and  throws  out  much  of  the  finely  divided  organic 
impurity.  The  apparatus  may  be  easily  modified  to  work  with 
alum  where  desirable.  The  water  from  Tis  said  to  be  sufficiently 
free  from  chemical  and  mechanical  impurity  for  all  practical  pur- 
poses. The  yield  of  the  apparatus  varies,,  according  to  its  size, 
•from  |  to  50  c.  m.  per  hour.  Larger  sizes  are  also  made  and 
we  are  informed  that  109  of  these  plants  are  in  use  in  Europe  at 
the  present  time. 


In  -ta'king  a  sample  of  water  for  analysis,  especially  if  any  opin- 
ion as  to  its  healthfulness  is  desired,  much  care  must  be  observed 
to  avoid  contamination  of  the  sample.  A  perfectly  clean  glass- 
stoppered  bottle  of  about  1  gallon  capacity  should  be  used.  The 
State  Board  of  Health  of  Massachusetts  has  issued  the  following 

INSTRUCTIONS  FOR  COLLECTING  SAMPLES  OF  WATER  FOR 

ANALYSIS. 

1.  From  a  Water  Tap. —  The  water  should  run  freely  from 
the  tap  for  a  few  minutes  before  it  is  collected.  The  bottle  is 
then  to  be  placed  directly  under  the  tap,  and  rinsed  out  with 
water  three  times,  pouring  out  the  water  completely  each  time. 
It  is  then  again  to  be  placed  under  the  tap,  filled  to  overflowing-, 
and  a  small  quantity  poured  out,  so  that  there  shall  be  left  an  air- 
space under  the  stopper  of  about  an  inch.  The  stopper  must  be 
rinsed  off  with  flowing  water  and  inserted  into  the  bottle  while 
still  wet,  and  secured  by  tying  over  it  a  clean  piece  of  cotton 
cloth,  The  ends  of  the  string  must  be  sealed  on  the  top  of  the 
stopper.  Under  no  circumstances  must  the  inside  of  the  neck  of 


WATER.  347 


the  bottle  or  the  stem  of  the  stopper  be  touched  by  the  hand  or 
wiped  with  a  cloth. 

2.  From  a  Stream,  Pond,  or  Reservoir.  —  The  bottle  and  stop- 
per should  be  rinsed  with  the  water,  if  this  can  be  done  without 
stirring  up  the  sediment  on  the  bottom.  The  bottle,  with  the 
stopper  in  place,  should  then  be  entirely  submerged  in  the  water, 
and  the  stopper  taken  out  at  a  distance  of  12  inches  or  more  below 
the  surface.  When  the  bottle  is  full,  the  stopper  is  replaced 
below  the  surface  if  possible,  and  finally  secured  as  above.  It 
will  be  found  convenient,  in  taking  samples  in  this  way,  to  have 
the  bottle  weighted,  so  that  it  will  sink  below  the  surface.  It  is 
important  that  the  sample  should  be  obtained  free  from  the  sedi- 
ment on  the  bottom  of  a  stream  and  from  the  scum  em  the  sur- 
face. If  a  stream  should  not  be  deep  enough  to  admit  of  this 
method  of  taking  a  sample,  the  water  must  be  dipped  off  with  an 
absolutely  clean  vessel,  and  poured  into  the  bottle  after  it  has 
been  rinsed. 

The  sample  of  water  should  be  collected  immediately  before 
shipping  by  express,  so  that  as  little  time  as  possible  shall  inter- 
vene between  the  collection  of  the  sample  and  its  examination. 

In  case  there  are  any  abnormal  or  unusual  conditions  existing 
in  the  source  of  the  water,  mention  the  facts :  as,  for  instance,  if 
the  streams  or  ponds  are  swollen  by  recent  heavy  rains;  or  are 
unusually  low  in  consequence  of  prolonged  drought ;  or  if  there 
is  a  great  deal  of  vegetable  growth  in  or  on  the  surface  of  the 
water. 


348 


THE  CHEMISTRY  OF  PAPER-MAKING. 


CHAPTER   VIII. 

CHEMICAL    ANALYSIS. 

UNDER  this  head  we  shall  make  no  attempt  to  map  out  elaborate 
methods  for  the  complete  analysis  of  the  different  substances 
named,  except  in  special  instances,  as  such  a  course  would  clearly 
be  beyond  the  scope  of  the  present  work.  It  would  also,  in  many 
cases,  call  for  more  or  less  complicated  and  expensive  apparatus, 
as  well  as  a  skill  in  chemical  manipulation,  which  one  could  only 
expect  to  find  in  the  well-equipped  laboratory  of  the  professional 
chemist. 

There  are,  however,  very  many  tests  of  value  which  may  be 
readily  applied  by  one  not  specially  skilled  in  analytical  methods, 
and  which  require  for  their  application  but  a  limited  amount  of 
apparatus.  Such  tests,  if  carefully  carried  out,  will  Tery  often 
serve  the  manufacturer's  purpose  quite  as  well  as  a  more  extended 
analysis,  and  at  other  times  may  indicate  the  desirability  of  such 
analyses. 

Our  purpose  here,  then,  is  to  bring  together  certain  easily 
applied  and  reliable  tests  for  ascertaining  the  purity  or  "  strength  " 

of  the  chemicals  more  or  less 
directly  concerned  hi  the  art 
of  paper-  making,  la  some 
few  instances,  for  example, 
alums  and  sulphite  liquors, 
we  have  thought  it  well  to 
lay  down  a  plan  for  the  com- 
plete analysis  of  the  sub- 
stance. 

The  apparatus  required  for 
preparing  the  necessary  solu- 
tions, and  making  the  tests 
named,  consists  of :  — 
1.   A  balance  (Fig.  78),  sensitive  to  ^.milligramme,  and  capable 
of  carrying  a  maximum  load  of  200  grammes  in  each  pan.    The 


FIG.  78.  —  ANALYTICAL  BALANCE. 


CHEMICAL  ANALYSIS. 


349 


FIG.  79. — MEASURING  FLASKS. 


balance  should  be  enclosed  in  a  glass  case  to  protect  it  from  dust 
and  acid  vapors,  as  well  as  from  drafts  of  air  while  weighing. 

2.  A  set  of  weights  ranging  from  a  100-gram  me  piece  to  a 
1 -milligram  me  piece.     These  should  be  kept  in  a  box  with  a  tight- 
fitting  cover  for  protection  from 

dust  and  dampness. 

3.  Measuring-flasks  (Fig.  79), 
holding  respectively  1000  c.c., 
500  c.c.,  250  c.c.,  100  c.c.,  and 
50  c.c.,  when  filled  to  the  mark 
engraved  on  the  neck. 

4.  Two  burettes,  which  are 
simply  straight  tubes  of  glass 
graduated  into   cubic   centime- 
tres and  tenths  of  cubic  centi- 
metres.    The   most  convenient 
size  holds  50  c.c.     One  of  these 

(Fig.  80),  is  narrowed  at  its  lower  extremity,  and  is  to  be  fitted 
with  a  piece  of  rubber  tubing  about  2  inches  long,  one  end  of. 
which  is  slipped  over  the  narrowed  end  of  the  burette,  while  the 
lower  end  of  the  tubing  carries  a  short  piece  of  glass  tube  which 

has  been  drawn  out  to  a  fine  point. 
By  means  of  a  spring-clip,  or  pinch- 
cock,  which  pinches  the  rubber  just 
above  the  glass  tip,  any  desired  quan- 
tity of  the  liquid  in  the  tube  may  be 
run  out. 

The  other  burette  should  be  provided 
with  a  glass  cock,  and  is  used  to  contain 
such  liquids  as  would  act  upon  rubber 
and  be  injuriously  affected  by  it,  as 
caustic  soda  or  iodine  solutions. 

The  manner  of  using  these  instru- 
ments will  be  shown  farther  on. 

5.  A  burette  stand  like  that  shown 
in  Fig.  80,  or  some  arrangement  for 
holding  'burettes  firmly  in  a  perpen- 
dicular position,  and  which  will  at  the 
same  time  permit  their  ready  removal  for  cleaning  and  filling. 
A  simple  screw  clamp  of  wood  or  iron  lined  with  cork  fixed  firmly 


FIG.  80. 


360 


THE  CHEMISTRY  OF 


to  aa  upright,  or  to  the  wall  of  the  room,  answers  the  purpose 
well. 

6.   Plain  flasks,  ungraduated,  of  different  sizes,  ranging  in  capac- 
ity, perhaps,  from  2  or  4  oz.  to  32  oz. 


FIG.  81. 

7.  Beaker  glasses  (Fig.  81)  of  different  sizes.     These  are  by 
preference  of  the  low  wide  form  with  lip  for  convenience  in  pour- 
ing.    They  are  known  as  Griffin's  beakers.      They  may  best  be 
obtained  in  nests  as  shown  in  the  figure.     Sizes  holding  from  4  oz. 
to  20  oz.  are  the  most  convenient. 

8.  Convex  glasses  known  as  clock  glasses.     These  are  to  serve 


FIG.  82. 


FIG. 


FIG.  84. 


as  covers  for  the  beakers  when  required,  and  the  sizes  should 
be  chosen  with  that  end  in  view.  They  serve  also  for  use  in 
weighing  such  substances  as  iodine,  which  would  injure  the  bal- 
ance pan  if  placed  directly  upon  it. 

9.  A  number  of  pieces  of  solid  glass 
rod  6  to  8  inches  in  length,  with  the 
ends  rounded  by  fusing   in   a  flame. 
These  are  for  use  as  stirrers. 

10.  Crucibles,  with  covers,  of  Royal 
Berlin    porcelain,    1|    inch    diameter 
(Fig.  8SQ.     Also  2  or  3  each  of  dif- 
ferent    sizes     of     evaporating-dishes 

(Fig.  88)  of  the  same  ware.  Two  or  three  casseroles  (Fig. 
84)  will  also  be  found  convenient 


FIG.  85. 


CHEMICAL  ANALYSIS. 


351 


11.  A  copper  water-bath  (Fig.  85),  6  inches  in  diameter,  for  use 
with  the  dishes  last  named. 

12.  A  ring  stand  (Fig.  86)  to  support  dishes  and  crucibles  while 
being  heated.     An  iron  tripod  is  also  needed  to 

support  the  water-bath. 

13.  Two  or   three  lamps  for  gas  or  alcohol, 
a*  the  case  may  be.     Where  gas  cannot  be  had, 
the    Kellogg   gasoline   lamp   for   laboratory   use 
gives  excellent   satisfaction,  and   with  ordinary 
care    is   free   from    danger.      Where   alcohol   is 
employed  for  heating,  a  Russian  blast  lamp,  so- 
called,  is  a  convenience  and  often  almost  a  ne- 
cessity. 

14.  Glass   funnels   of   60°   angle.    2,    4,    and 

6-inch  diameters  are  convenient  sizes.  FlG-  86- 

15.  A  4-inch  porcelain  mortar  for  grind- 
ing samples,  etc. 

16.  An  evaporating-dish  of  platinum  hold- 
ing 50  to  100  c.c.,  and  a  crucible  of  the  same 
metal  of  15  to  20  e.c.,- capacity  with  a  cover; 
also  a  triangle   of   stout   platinum  wire  for 
supporting  crucibles  over  the  flame. 

17.  A  set  of  reagent  bottles,  and  several 
green  glass   bottles,   holding  £-  gallon  each, 
with    glass    stoppers,   for    holding   standard 
solutions. 

18.  A  dozen  or  two  of  6-inch  test-tubes, 
which  for  convenience  in  shaking  should  be  not  too  wide  to  be 
easily  covered  by  the  thumb,  some 

tubing  of  soft  glass  of  about  ^-inch 
bore,  with  a  few  feet  of  rubber  tub- 
ing to  match ;  a  desiccator  (Fig.  87) 
and  a  pair  of  crucible  tongs  (Fig. 
88)  make  up  the  list  of  apparatus. 
The  manner  in  which  these  various 
pieces  of  apparatus  are  to  be  used  yrill  he  explained  as  they 
are  called  for  in  the  tests  which  follow. 


Firu  $7. 


Fie.  88. 


352  THE  CHEMISTRY  OF  PAPER-MAKING. 


NORMAL   SOLUTIONS. 

In  the  testing  of  certain  substances,  notably  aoids  and  alkalies, 
it  is  often  most  convenient  to  calculate  their  strength  by  ascer- 
taining the  quantity  of  a  solution,  the  strength  of  which  is  known 
beforehand,  it  will  take  to  neutralize  or  balance  a  definite  quantity 
of  the  solution  to  be  tested. 

In  such  instances  the  test  solution  is  called  a  standard  solution, 
and  is  always  either  made  and  used  of  an  exact  and  definite 
strength  known  as  normal  strength,  or  the  actual  volume  em- 
ployed of  a  strength  other  than  normal  is  reduced  in  the  calcu- 
lation to  the  equivalent  volume  of  normal  strength  by  the  use  of 
a  previously  ascertained  factor.  Normal  solutions  then  are  always 
made  on  the  simple  and  definite  plan  of  having  each  1000  c.c.  of 
solution  contain  the  number  of  grammes  of  pure  substance  repre- 
sented by  the  molecular  weight  of  that  substance  if  its  valency  is 
one,  one-half  the  molecular  weight  if  the  valency  of  the  substance 
is  two,  one-third  if  the  valency  is  three,  etc.  Thus,  for  example, 
to  make  a  normal  solution  of  sodium  hydrate,  NaHO,  the  val- 
ency of  which  is  one,  and  its  molecular  weight  40  (Na  23  -f-  H  1  -f 
0 16  =  40),  40  grammes  of  NaHO  must  be  dissolved  to  make  1000  c.c. 
of  solution. 

To  make  normal  sulphuric  acid  we  dilute  one-half  the  molec- 
ular weight  in  grammes  to  1000  c.c.,  since  sulphuric  acid  is  a 
bivalent  acid,  or  in  figures  H2SO4  =  molecular  weight  98,  -4-2  =  49 
grammes  to  the  litre.  The  initial  N  is  commonly  used  as  an  ab- 
breviation for  normal.  When  made  upon  this  plan  it  will  always 
be  found  that  equal  quantities  by  volume  of  any  two  normal  solu- 
tions whose  chemical  properties  are  opposite  will  exactly  balance  or 
neutralize  each  other.  For  example,  100  c.c.  N  of  soda  solution 
will  exactly  neutralize  100  c.c.  N  of  sulphuric,  or  a  like  amount 
of  any  other  normal  acid  solution.  Again,  50  c.c.  of  normal  arsenic 
solution  will  exactly  neutralize  50  c.c.  of  normal  iodine.  In  prac- 
tice it  is  difficult  in  most  cases  to  make  a  strictly  normal  solution 
on  account  of  slight  impurities  often  present  in  so-called  chemically 
pure  chemicals,  and  the  difficulty  of  accurately  weighing  many 
substances.  It  is  usually  much  more  convenient  to  weigh  approxi- 
mately the  required  number  of  grammes  per  litre  of  ths  substance 
in  hand,  and  after  the  solution  has  been  made  up  to  volume,  to 


ACTUAL  ANALYSIS.  853 


accurately  determine  by  appropriate  means  the  actual  amount  of 
the  given  substance  it  contains  per  cubic  centimetre,  and  this  done 
it  is  easy  to  find  a  factor  by  means  of  which  to  reduce  any  number 
of  c.c,  of  this  solution  to  equivalent  c.c.  of  normal  solution.  For 
example,  we  have  made  up  a  solution  of  caustic  soda  (NallO) 
and  find  that  it  contains  0:0398  grammes  of  NaHO  per  cubic  centi- 
metre, instead  of  0.0400  grammes,  which  a  strictly  normal  solution 
would  contain. 

Then  to  find  the  factor  for  reducing  this  solution  the  proportion 
should  be,  as  0.04  (normal  solution)  is  to  0.0398  (our  solution),  so 
is  1  c.c.  to  x  <0.04: 0.0398  =  1:  x =0.995),  and  we  find  the  factor 
to  be  0.995.  In  other  words,  100  c.c.  of  our  solution  equals  99| 
c.c.  of  normal  solution. 

The  method  of  analysis  by  the  use  of  normal  solutions  is  called 
volumetric  analysis,  in  distinction  from  gravimetric  analysis,  in 
which  latter  the  substance  to  be  estimated  is  converted  into  some 
definite  compound  insoluble  in  the  given  menstruum,  and  which  is 
then  separated,  dried,  and  weighed,  when,  from  the  weight  of  the 
compound,  that  of  the  substance  wanted  is  calculated.  In  gravi- 
metric analysis,  the  exact  strength  of  the  reagent  solutions 
employed  is  not  necessarily  known. 

In  every  method  of  chemical  analysis,  cleanliness  of  apparatus 
employed,  and  the  utmost  care  to  guard  against  loss,  and  to  secure 
accuracy  in  weighing  and  measuring,  are  essential  in  order  to 
secure  reliable  results. 


ACTUAL    ANALYSIS. 

ACIDS. 

Unite  with  alkalis  and  metallic  salts,  -r-  Solutions  in  water  turn  litmus  red. 

/Sulphuric  Acid  (Oil  of  Vitriol). 

Symbol,  H,^SO4.-- Valency,  TI.  — Molecular  weight,  98. 

For  specific  gravity  of  solutions  of  H2SO4,  and  percentage  of  actual  H2SO4  con- 
tained, see  Appendix. 

The  presence  of  sulphuric  acid,  either  free  or  in  combination, 
may  be  recognized  in  solution  by  means  of  barium  chloride  solu- 
tion, which  forms,  with  sulphuric  acid,  or  soluble  sulphates,  a 
heavy,  white,  very  finely  divided  compound  of  barium  sulphate 


354  THE  CHEMISTRY  OF.  PAPER-MAKING. 

(BaSO4).  This  compound  is  insoluble  in  water,  and  very  nearly 
so  in  dilute  hydrochloric  acid,  even  on  boiling.  It  is  soluble  only 
very  sparingly  in  strong  boiling  hydrochloric  acid. 

Free  sulphuric  acid  in  a  solution  not  containing  other  free  acids 
may  be  estimated  volume trically  by  means  of  standard  soda  solu- 
tion as  follows :  — 

Forty-nine  grammes  are  weighed  in  a  beaker,  and  made  to  10.00 
c.c.  with  water*  and  the  solution  well  shaken  up.  The  beaker  should. 
be  rinsed  several  times  with  water,  and  the  rinsings  poured  into 
the  1000  c.e.  flask,  which  «is  then  filled  to  the  mark,  and  ..shaken. 
100  c.c.  of  this-  solution  are  then  measured  out  in  the  100  c.c. 
measuring  flask,  and  transferred  to  a  beaker,  or  porcelain  dish, 
and  the  small"  flask  rinsed  several  times  with  water,  the  rinsings 
being  added  to  the  liquid  in  the  beaker.  A  few  drops  of  litmus 
solution  .are  added,  and  the  whole  warmed  over  the  lamp.  While 
the  solution  is  warming,  a  burette  with  rubber  tip  should  be  filled 
just  to  the  zero  mark  with  standard  soda  solution.-  When  the  acid 
solution  in  the  beaker  has  come  to  a  boiling  heat,  the  soda  solution 
from  the  burette  is  run  in,  a  little  at  a  time,  stirring  the  contents 
of  the  glass -after  each  addition  until  the  color  of  the  solution  lias 
just  ciianged  from  the  red,  which  it  has  previously  exhibited,  to  a 
purple  tint.  The  number  of  cubic  centimetres,  and  tenths  of  cubic 
centimetres,  of  soda  solution  used  is  now  read  off  from  the  burette, 
and  converted,  by  means  of  the  appropriate  factor,  into  normal 
cubic  centimetres.  The  number  of  normal  cubic  centime tree 
employed  represents  directly  the  percentage  of  HaSO4  in  the 
original  solution,  a  portion  of  which  was  weighed  out  for  the  test. 
If  the  solution  to  be  tested  is  weak,  it  is  convenient  to  weigh 
twice,  or  three  times,  the  amount  named  above  (49  grammes),  and 
dilute  it  to  1000  c.c.,  taking  100  c.c.  of  this  solution,  as  before,  for 
the  actual  test.  In  such  case,  of  course,  the  number  of  normal 
cubic  centimetres  employed  must  be  divided  by  2,  or  3,  as  the  case 
may  be,  to  give  the  per  cent. 

When  free  acids,  other  than  sulphuric  acid,  are  present  with 
the  latter  in  solution,  the  amount  of  this  acid -cannot  be  estimated 
by  means  of  standard  soda,  but  it  must  be  separated  and  weighed, 
as  in  the  estimation  of  sulphuric  acid  m  Sulphate*  below,  which 
see. 

The  impurities  to  be  looked  for  in  commercial  oil  of  vitriol  are 
lead,  arsenic,  .nitric  and  nitrous  .acids,  and  occasionally  ammonia. 


ACTUAL.  ANALYSIS.  355 


Hydrochloric  Acid  (Muriatic  Acid). 

Symbol,  HCI.  —  Valency  I.  —  Molecular  weight,  36.5. 

For  specific  gravity  of  solutions  and  percentage  of  HCi  contained,  see  Appendix. 

Hydrochloric  acid  may  be  recognized  jm  solution,  either  when 
free  or  combined  with  bases,  by  means  of  solution  of  silver  nitrate. 
When  eolation  of  silver  nitrate  is  added  to  a  solution  containing 
HCI,  or  chlorides  previously  acidified  by  the  addition  of  a  feiv 
drops  only  of  nitric  acid,  a  white,  curdy  precipitate  of  silver  chloride 
is  formed  which  is  insoluble  in  dilute  nitric-  acid,  either  cold  or  hot. 
It  is  slightly  soluble  in  strong  nitric  acid,  and  readily  dissolved  by 
ammonia  water.  The  white  chloride  of  silver  precipitate,  when 
exposed  to  strong  daylight,  rapidly  turns  purple,  and  after  a  little 
time  becomes  nearly  black.  If  much  organic  matter  is  present  in 
the  solution  tested,  it  often  interferes  with  the  above  reaction,  and 
may  obscure  it  entirely  by  the  formation  of  a  black  precipitate. 
In  this  case  the  solution  must  be  evaporated  to  dryness,  and  gently 
ignited  to  carbonize  the  organic  matter.  It  is  then  treated  with 
water,  and  the  resulting  solution  filtered  and  tested  with  silver 
nitrate. 

Free  hydrochloric  acid  in  solution,  other  free  acids  not  being 
present,  may  be  estimated  by  means  of  standard  soda  solution. 
For  this  purpose  36.5  grammes  of  the  solution  are  weighed  out 
and  made  to  1000  c.c.,  as  in  testing  Sulphuric  Acid  above,  which 
see.  100  c.c.  of  the  prepared  solution  are  transferred  to  a  beaker, 
or  porcelain  dish,  as  above,  colored  with  litmus  solution  and 
standard  soda  solution  run  in  from  the  burette,  until  nearly  all  the 
acid  is  neutralized.  The  solution  is  then  heated  to  boiling,  and 
the  soda  solution  dropped  in  until  the  purple  color  appears.  The 
number  of  cubic  centimetres  of  soda  solution  used  represents 
directly,  after  reduction  to  normal  cubic  centimetres  by  means  of 
the  appropriate  factor,  the  percentage  of  HCI  in  the  original  solu- 
tion weighed  out. 

To  estimate  HCI  in  solution  with  other  free  acids  it  must  be 
separated  and  weighed  as  silver  chloride,  or,  after  neutralization, 
titrated  with  standard  silver  nitrate  solution.  For  details  of  both 
these  methods,  see  under  Chlorides,  below. 

The  impurities  to  be  looked  for  in .  commercial  muriatic  acid  are, 
sulphuric  acid  (sulphurous  acid  occasionally),  iron,  and  other 
metals,  and  frequently  arsenic  in  small  .amount. 


356  THE  CHEMISTRY   OF  PAPER-MAKING. 

Nitric  Acid  {Aqua  fortis"). 

Symbol,  HNO8.  —  Valency,  I.  —  Molecular  weight,  63, 

For  specific  gravity  of  solutions  and  percentage  of  HNOS  contained,  see  Appendix. 

Free  or  combined  HNO3  may  be  recognized  in  solution  by 
means  of  ferrous  sulphate.  To  test  for  HNO3,  a  small  amount 
of  the  liquid  should  be  taken  in  a  test-tube,  and  about  an  equal 
volume  of  strong  H2SO4  added  cautiously.  The  whole  should 
then  be  mixed  by  means  of  a  glass  rod,  and  cooled  quickly  by 
placing  the  tube  in  water.  When  cool,  a  small  piece  of  ferrous 
sulphate  should  be  dropped  into  the  tube,  care  being  taken  to 
select  a  fragment  of  crystal  which  is  of  a  clear  green  color,  with 
no  powdery  whitish  substance  upon  it.  If  HNO8  is  present,  a 
purplish  zone  will  form  after  a  few  moments  about  the  fragment 
of  ferrous  sulphate,  while  in  the  absence  of  HNO3,  the  entire 
solution  will  remain  unchanged.  Instead  of  a  fragment:  of  the 
salt,  a  freshly  made  solution  of  ferrous  sulphate  may  be  employed. 
By  inclining  the  tube  containing  the  liquid  to  be  tested,  the 
ferrous  solution  may  be  carefully  poured  down  the  side  so  as  not 
to  mix  with  the  solution  in  the  tube.  On  again  bringing  the  tuhe 
into  an  upright  position,  a  purple  zone  will  appear  at  the  line  of 
junction  of  the  two  liquids  when  HNO3  is  present,  and  on  shaking 
the  tube  so  as  to  mix  the  contents,  the  whole  solution  will  be  more 
or  less  darkened.  A  few  experiments  with  solutions  known  to 
contain  HNO3,  in  comparison  with  those  known  not  to  contain  it, 
will  be  useful  in  familiarizing  one  with  the  appearance  of  the  test, 
and  in  enabling  one  to  acquire  the  moderate  skill  necessary  to 
make  it  successful. 

Nitric  acid  in  solution,  when  other  free  acids  are  absent,  may  be 
estimated  with  standard  soda  solution,  the  details  of  the  process 
being  precisely  the  same  as  in  the  case  of  Hydrochloric  Acid,  which 
see ;  the  proper  amount  of  solution  to  be  weighed  in  this  case 
being  63  grammes  to  be  diluted  to  1000  c.c. 

The  estimation  of  HNO3  when  mixed  with  other  acids,  or  when 
in  combination,  presents  certain  difficulties  and  calls  for  special 
apparatus.  When  this  estimation  seems  called  for  the  sample  had 
better  be  sent  to  a  reliable  analyst. 

The  impurities  to  be  looked  for  in  commercial  nitric  acid 
("  aqua  fortis ")  are  hydrochloric  and  sulphuric  aeids  and 
metals. 


ACTUAL  ANALYSIS.  857 


ACETIC   ACID. 
Pyroligneous  Acid  {Wood  Vinegar). 

Symbol,  C2H4O2.  —  Valency,  I.  —  Molecular  weight,  60. 
For  specific  gravity  of  solutions  and  percentage  of  C2H4O3  contained,  see 
Appendix. 

Free  acetic  acid,  unless  present  in  quite  small  amount,  snay 
usually  be  recognized  by  its  vinegar  odor,  more  pronounced  on 
warming.  When  present  in  too  small  a  quantity  to  be  recogniz- 
able by  the  above  means,  or  when  in  combination,  it  may  be  con- 
verted into  acetic  ether,  which  is  a  very  volatile  substance  having  a 
very  distinctive  and  penetrating  though  not  unpleasant  odor.  To 
perform  the  test  a  small  portion  of  the  liquid  to  be  tested  is  placed 
in  a  test-tube.  About  one-half  its  volume  of  alcohol  is  added, 
and  an  equal  amount  of  strong  sulphuric  acid,  and  the  whole  well 
mixed.  If  acetic  acid  (or  acetates)  were  present  in  the  solution, 
the  odor  of  acetic  ether  will  be  apparent  either  at  once,  or  will 
become  so  on  heating  the  contents  of  the  tube  to  boiling  over  a 
lamp. 

In  order  to  familiarize  oneself  with  the  odor  of  acetic  ether  so 
as  to  be  able  to  recognize  it,  it  will  be  well  to  make  the  test  as 
above  upon  a  solution  of  sodium  acetate  containing  from  2  to 
5  grammes  of  the  salt  in  100  c.c. 

Free  acetic  acid  in  solution,  apart  from  other  free  acids,  may  be 
estimated  by  titration  with  standard  soda  solution  in  the  manner 
given  in  detail  under  Hydrochloric  Acid,  above.  The  proper 
amount  to  be  weighed  in  this  case  is  60  grammes  to  be  made  to 
1000  c.c.  The  number  of  cubic  centimetres  of  normal  soda  solu- 
tion consumed  or  neutralized  by  100  c.c.  of  the  diluted  solution 
then  equals  per  cents,  of  C2H4O2  in  the  original  solution  to  be 
tested. 

It  should  be  borne  in  mind  that  in  titrating  .acetic  acid,  when 
litmus  solution  is  employed  as  the  indicator  of  the  saturation 
point,  soda  solution  should  be  added  until:  the  liquid  is  a  full  blue, 
instead  of  stopping  when  the  purple  tint  is  reached,  as  in  the. 
titration  of  the  acids  previously  mentioned. 

On  this  accouiit,  we  prefer  to  employ  a  solution  of  phenol- 
phtalein  as  indicator  in  the  present  case.  To  make  this  solution, 
<X200  grammes  (about)  of  phenolphtalem  should  be  dissolved  in 


868  THE  CHEMISTRY  OF  PAPER-MAKING. 

100  c.c.  of  moderately  strong  alcohol,  arid  the  solution  filtered  if 
not  clear.  To  thi§  solution  weak  caustic  soda  solution  is  added 
until  a  very  faint  rose  color  remains  after  shaking.  The  solution 
is  then  ready  for  use.  It  should  be  kept  well  corked.  About  10 
to  15  drops  of  this  solution  are  to  be  added  to  the  portion  of  acid 
solution  used  for  the  titration.  The  soda  solution  should  then 
bo  added  until  a  brilliant  rose  purple  coloration  appears  which 
remains  permanent  after  stirring.  This  indicates  that  the  acid 
has  all  been  neutralized,  since  the  color  only  appears  in  the 
presence  of  alkali,  but  the  presence  of  even  the  most  minute 
quantity  of  free  alkali  is  sufficient  to  develop  a  brilliant  color. 
For  the  estimation  of  acetic  acid  in  combination,  see  Acetates. 

Impurities  in  commercial  acetic  acid  are  muriatic  acid,  acetates 
of  soda  and  lime,  acetate  of  methyl,  and  empyreumatic  (organic) 
matter. 

Oxalic  Aoid. 
Symbol,  H2C3O4,  2  H2O.  —  Valency,  II.  —  Molecular  weight,  126. 

Oxalic  acid  free,  or  in  combination  with  alkalis,  may  be  recog- 
nized in  solution  by  means  of  calcium  sulphate  solution.  The 
solution  to  be  tested  should  be  rendered  alkaline  by  the  addition 
of  ammonia  in  excess.  It  is  then  filtered  if  necessary,  and  solution 
of  calcium  sulphate  added.  If  oxalic  acid,  or  an  oxalate,  is  present, 
this  will  produce  a  fine  white  cloud  or  precipitate  easily  redissolved 
by  hydrochloric  acid  in  excess,  and  again  appearing  on  addition  of 
excess  of  ammonia  water.  Free  oxalic  acid  may  be  estimated 
by  titration  with  standard  soda  solution  as  in  the  preceding 
paragraphs. 

The  proper  amount  of  tfoe  solution  to  be  weighed  is  63  grammes 
to  be  made  to  1000  c.c. 

If  the  crystallized  acid  is  to  be  tested,  it  is  as  well  to  weigh  one- 
half  the  above  amount,  and  make  to  1000  c.c.,  and  take  100  c.c.  of 
this  solution  for  titration.  Of  course,  in  this  case  the  number  of 
cubic  centimetres  of  normal  soda  used  must  be  doubled  to  give 
the  percentage  of  actual  crystallized  acid  in  the  sample. 

Either  litmus  or  phenolphtalein  solution  may  be  employed  as 
indicator  with  oxalic  acid,  and  no  precautions  need  be  taken  to 
nearly  neutralize  with  soda  solution  before  heating  as  in  the  ease 
of  hydrochloric  and  nitric  acids,  since  this  acid  is  not  iu  the 


ACTUAL   ANALYSIS.  359 


least  volatile  from  its  solution,  as  is  the  case  with  the  acids  last 
mentioned. 

ALKALIS   AND   ALKALINE  EARTHS. 
Unite  with  acids  to  form  salts.  —  Solutions  of  the  alkalis  turn  litmus  blue. 

Sodium  Hydrate  ^Gamtie  Soda). 

Symbol,,  NaHO.  —  Valency,  I.  —  Molecular  weight,  40.  , 

JKor  specific  gravity  of  solutions  and  percentage  of  NaHO  contained,  see  Appendix. 

It  is  difficult  to  apply  tests  to  a  solution  of  caustic  soda  or  of 
soda  salts  which  shall  give  direct  evidence  of  the  presence  of  soda 
as  distinct  frora  other  alkalis.  Perhaps  the  best  ready  qualitative 
test  for  soda  lies,  in  the  intense  yellow  color  given  to  the  flame  of 
an  alcohol  lamp  or  Bunsen  burner  when  a  platinum  wire  moistened 
with  the  -solution  to  be  tested  is  held  in  the  flame.  This  test  is, 
however,  of  such  extreme  delicacy,  and  the  presence  of  compounds 
of  soda  in  the  minute  quantities  required  to  produce  the  yellow 
flame  so  well-nigh  universal,  as  to  render  this  test  of  little  practical 
value.  Probably  the  easiest  way  to  prove  the  presence  of  soda  in 
an  alkaline  solution  is  to  work  backwards  and  prove  that  it  is  not 
one  of  five  other  alkalis  (appropriate  tests  for  'which  will  be 
described  under  their  respective  heads),  and  consequently  must  be 
soda. 

There  are  several  direct  tests  which  can  be  applied  to  prove  the 
presence  of  soda  or  its  salts;  but  as  they  require  very  careful 
manipulation  to  render  their  indications  reliable,  we  have  thought 
it  best  not  to  describe  them  here. 

Quantitative.  — In  a  simple  solution  of  caustic  soda  -not  con- 
tain ing  other  alkalis  the  percentage  of  soda,  NaMO,  may  be  easily 
determined  by  tjitration  with  standard  acid  solution.  For  this 
purpose  a  standard  sulphuric  acid  of  about  normal  strength 
(49  grammes  H2SO4  per  litre.)  is  perhaps  best.  Standard  oxalic 
aoid  also  answers  the  purpose  well.. 

Foyty  grammes  of  the  soda  solution  or-ithe  solid  substance  caustic 
soda  are  to  be  weighed,  and  its  solution  made  to  1000  e.c.;  100  c.c. 
of  this  solution  is,  if  not  entirely  clear,  filtered  through  a  dry  filter, 
since,  if  the  filter  were  previously  wet  with  water,  it  would  dilute 
to  ft  certain  extent  the  100  c.c,  passed  through  it.  The  filtrate  is 
transferred  to  a  beaker  or  casserole  and  colored  with  litmus  solu» 


360  THE  CHEMISTRY  OF  PAPER-MAKING. 

tion.  Standard  acid  is  run  in  from  the  burette  until  the  original 
blue  color  changes  to  purple.  The  liquid  is  then  boiled,  when  the 
blue  color  will  generally  again  appear.  Acid  is  again-  dropped  in 
from  the  burette,  a  drop  at  a  time,  boiling  for  a  moment  after  each 
addition,  until  the  liquid  shows  a  full  red  color,  and  no  trace  of 
blue  or  purple  appears  after  two  or  three  minutes'  boiling. 

The  number  of  cubic  centimetres  of  acid  employed*  reduced  to 
normal  cubic  centimetres  by  the  use  of  the  appropriate  factor, 
represents  the  percentage  of  caustic  soda,  NaHO,  in  the  sample 
tested. 

In  commercial  transactions  caustic  soda  is  usually  quoted  as  60 
or  70  per  cent,  alkali,  as  the  case  may  be. 

In  this  connection,  as  in  the  alkali  trade  generally,  the  term 
"alkali"  does  not  have  its  proper  chemical  significance,  but  signi- 
fies sodium  oxide,  Na3O,  or  we  may  call  it  anhydrous  caustic  soda. 
31  parts  by  weight  of  this  substance,  Na2O  ("alkali'*)  +  9  parts  of 
water  =  40  parts  of  sodium  hydrate  or  caustic  soda. 

This  being  the  case,  if  we  wish  to  find  the  per  cent,  of  "alkali," 
Na2O,  in  the  sample  tested  as  above,  we  must  multiply  the  per 
cent,  of  caustic  soda,  NaHO,  by  31  and  divide  the  product  by  40. 


In  Europe  an  arbitrary  custom  obtains  of  using  the  old  numbers 
32  and  41  in  place  of  the  corrected  ones  31  and  40  respectively  in 
all  instances  mentioned  above.  This  is  now  entirely  without  right 
or  reason,  and  is  oftentimes  annoying  to  the  American  buyer,  who 
finds  a  caustic  reported  as  72  per  cent,  alkali  by  the  English 
chemist  will  be  reported  only  69.75  per  cent,  by  the  American 
test,  which  gives  its  true  value.  Of  course,  when  one  is  aware 
of  the  custom,  it  is  eftsy  to  make  the  allowance;  but  in  the 
interests  of  truth  and  fair  dealing,  every  American  buyer  of  alkali, 
either  caustic  or  carbonated,  should  insist  that  payment  be  made 
on  the  basis  of  the  American  test. 

The  total  amount  of  soda,  Na2O,  present  in  a  given  solution, 
both  as  caustic  and  as  salts  of  soda,  is  determined  by  means  of  a 
long  and  somewhat  troublesome  series  of  eliminations,  by  means 
of  which  the  soda  is  finally  obtained  in  the  form  either  of  pure 
sulphate  or  chloride,  which  may  be  weighed  after  ignition,  and 
from  its  weight  the  soda  calculated. 


ACTUAL  ANALYSIS.  361 


Potassium  Hydrate  {Caustic  Potash). 

Symbol,  KHO.  —  Valency,  I.  —  Molecular  weight,  60. Jl. 

For  specific  gravities  of  solutions  and  per  cent,  of  KHO,  see  Appendix. 

Potash  may  be  recognized  in  solution  by  means  of  the  color-  it 
imparts  to  the  colorless  Bunsen  or  alcohol  flame.  The  color, 
except  when  the  proportion  of  potash  is  very  large,  is  usually 
masked  to  the  naked  eye  by  the  intense  yellow  color  of  the  sodium 
flame.  By  the  use  of  a  piece  of  blue  (cobalt)  glass  of  a  moderately 
deep  shade  the  yellow  color  of  the  sodium  flame  may  be  shut  out, 
as  it  were,  and  the  potash  flame  then  appears  through  the  glass  of 
a  beautiful  rose  color.  The  manner  of  applying  the  flame  test  is 
to  dip  the  end  of  a  small  platinum  wire  in  the  solution  to  be 
tested,  and  then  hold  it  in  the  flame  until  it  becomes  red  hot. 

Caustic  potash  in  solutions  not  containing  other  free  alkalis 
may  be  estimated  by  titration  with  standard  acid  in  exactly  the' 
same  way  as  caustic  soda  described  above. 

The  amount  to  be  weighed  out  is  56.1  grammes,  to  be  diluted 
to  1000  c.c.  The  number  of  normal  cubic  centimetres  of  acid  con- 
sumed by  100  c.c.  of  this  solution  equals  per  cents,  of  KHO. 

If  the  percentage  of  K2O  anhydrous  potash  is  required,  it  may 
be  obtained  by  multiplying  the  per  cents,  of  KHO  by  47.1,  and 
dividing  the  product  by  56.1. 

The  process  of  determining  accurately  the  total  amount  of 
potash  in  a  solution  containing  salts  of  potash  along  with  other 
substances,  as  with  soda,  is  long  and  tedious  to  one  not  thoroughly 
conversant  with  chemical  manipulations,  and  on  that  account  we 
omit  it  here. 

AMMONIUM  HYDRATE. 

Ammonia  (  Water  of  Ammonia'). 
Symbol,  NH4OH. 

Ammonia  is  usually  reckoned  and  reported  in  terms  of  anhy- 
drous ammonia  gas  ;  and  in  accordance  with  this  c.ustom  we  shall 
so  consider  it  in  this  paragraph. 

Symbol,  NH8.  —  Valency,  I.— -Molecular  weight,  17. 

For  tables  of  specific  gravity  of  solutions  and  percentage  of  ammonia  contained,  see 
Appendix. 

Free,  or  caustic,  ammonia,  being  a  volatile  alkali,  reveals  its 
presence,  either  at  once,  or  on  warming  the  solution,  by  its  char- 


362  THE  CHEMISTRY  OF  PAP£R-MAKING. 

acteristic  odor,  and  by  turning  a  piece  of  filter  paper,  moistened 
with  red  litmus  solution,  blue,  when  held  in  the  vapor  arising 
from  a  warmed  solution.  It  does  not  reveal  its  presence  in  this 
way  when  present  in  combination  with  an  acid ;  but  on  the  addi- 
tion of  a  sufficient  quantity  of  caustic  soda  solution  to  a  solution 
containing  any  salt  of  ammonia  it  may  be  at  once  detected,  as 
indicated  above. 

Caustic  ammonia  in  solution  not  containing  other  free  alkalis 
or  alkali  carbonates,  may  be  titrated  directly  with  standard  acid, 
as  indicated  under  Soda,  above. 

Ammonia  being-  a  volatile  alkali,  however,  the  solution  must 
be  titrated  without  heating. 

The  proper  amount  to  be  weighed  out  is  17  grammes  to  1000  c.c. 

For  the  determination  of  the  combined  ammonia  in  imy  liquid, 
it  is  sufficient,  after  having  made  up  to  1000  c.c.  as  above,  to  take 
100  c.c.  and  distil  after  adding  aa  excess  of  magnesium  oxide 
(caustic  magnesia),  MgO,  so  long  AS  any  ammonia  continues  to 
come  over  with  "the  steam.  This  usually  takes  from  one  to  two 
hours.  The  distillate  is  to  be  received  in  -a  flask  containing  a 
measured  number  of  c.c.  of  standard  acid  Which  must  be  more  than 
sufficient  to  neutralize  all  the  ammonia  which  may  distil  over. 
When  all  the  ammonia  has  been  distilled  into  the  acid,  t3ie  excess 
of  <acid  remaining  unneutralized  is  titrated  by  means  of  standard 
soda  and  litmus  —  the  difference  between  the  number  of  -normal 
cubic  centimetres  of  acid  employed  and  the  number  of  normal 
.orcMc  centimetres  of  soda  used  to  neutralize  the  excess  remaining 
equals  the  number  of  normal  cubic  centimetres  of  acid  neutralized 
by  the  ammonia,  or  per  cents,  of  NH3  in  the  sample. 

•Calcium  Hydrate  (Slaked  Limey. 

Symbol,  Ca-lljO,.— Valency,  II. — Molecular  weight,  74. 

POT  specific  gravity  of  solutions  and  milk  of  lime,  see  Appendix. 

Calcium  Oxide-,  —  Lime  (Caustic  Lime)* 
Symbol,  CaO.  —  Valency,  II.  —  Molecular  weight,  56. 

The  term  "lime"  or  u caustic  lime,"  as  commonly  employed, 
means  burned  lime  or  calcium  oxide,  CaO,  in  distinction  from 
slaked  lime,  which  is  calcium  hydrate,  CaH2O2,  or  the  former 
combined  with  water. 


LIME,  863 

Lime  may  be  recognized  in  solution  by  means  of  oxalate  of 
ammonia  solution  with  which  it  gives  a  fine  white  crystalline  pre- 
cipitate (compare  Oxalic  Acid,  above).  The  solution,  <o  be  tested 
should  first  be  rendered  alkaline  with  ammonia,  filtered  if  ammonia 
has  caused  a,  precipitate,  and  the  filtrate  tested  with  a  few  drops 
of  oxalate  of  ammonia. 

If  metallic  salts,  as  lead  acetate  or  zinc  sulphate  or  chloride, 
are  present,  the  metallic  oxides  must  be  removed  by  treatment  of 
the  solution,  after  the  addition  of  ammonia,  with  ammonium  sul- 
phide solution  and  filtering.  The  filtrate  is  then  tested  with  oxalate 
as  above.  A  good  method  for  testing  a  sample  of  burned  lime  or 
limestone,  which  is  easily  carried  out  and  which  with  care  will 
give  results  sufficiently  accurate  for  all  ordinary  purposes,  is  as 
follows.  A  considerable  amount,  say  a  pound  or  two,  of  the  lime 
should  be  picked  out  to  represent  as  fairly  as  possible  the  average 
quality  of  the  lot.  This  should  be  broken  down  into  small  bits 
not  larger  than  peas.  The  whole  is  then  well  mixed,  and  an 
ounce  or  two  taken  out  for  the  working  sample.  This  small 
sample  should  be  ground  in  a  porcelain  mortar  sufficiently  fine  to 
pass  a  No.  24  sieve,  and  the  resulting  powder  again  well  mixed 
and  preserved  in  a  well-closed  bottle. 

For  the  actual  analysis,  5  grammes  of  the  powder  are  to  be 
weighed  out  and  transferred  to  a  beaker;  about  50  c.c.  of  water 
are  then  poured  on  it,  and  sufficient  hydrochloric  acid  to  dissolve 
the  sample  (about  25  c.c.  will  be  sufficient),  and  the  whole  boiled. 
This  treatment  will  dissolve  the  entire  sample  with  the  exception 
of  the  silica,  SiO3,  which  is  to  be  filtered  out  on  a  small  filter,  well 
washed  with  hot  water,  dried,  transferred  to  a  platinum  crucible 
together  with  the  filter,  and  ignited  strongly,  and  after  cooling 
weighed, 

Th0  weight  found  calculated  to  per  cents,  gives  sand  and  silica, 
insoluble  in  acid,  in  the  sample. 

The  solution  filtered  from  the  above,  together  with  the  washings 
from  the  same,  is  next  to  be  heated,  and  ammonia  water  added 
cautiously  until  the  odor  of  ammonia  is  just  perceptible  in  the 
liquid  after  stirring.  The  solution  is  then  to  be  kept  very  near 
to  the  boiling-point  for  some  time  until  all  the  smell  of  ammonia 
has  disappeared.  This  treatment  separates  the  alumina  and 
sesquioxide  of  iron  present;  The  solution  is  next  to  be  filtered, 
aad  the  precipitate  well  washed  with  hot  water.  The  residue  of 


864  THE  CHEMISTRY  OF  PAPER-MAKING. 

A12O3  and  F2O3  on  the  filter  is  to  be  thoroughly  dried  and  then 
ignited  in  the  platinum  crucible,  together  with  the  filter,  and 
weighed  after  cooling,  and  the  weight  calculated  into  per  cents. 

The  filtrate  and  washings  from  the  alumina  and  iron  oxide 
precipitate  is  next  made  to  500  c.c.  Then  50  c.c.  of  this,  which 
equals  0.5  grammes  of  the  original  sample,  is  transferred  to  the 
platinum  evaporating-dish,  which  has  been  previously  cleaned, 
ignited,  and  weighed.  The  contents  of  the  dish  are  evaporated  to 
dryness  on  the  water-bath,  and  ignited  (carefully,  to  avoid  spatter- 
ing and  consequent  loss)  at  a  moderate  heat  until  no  more  fumes 
come  off.  The  dish  is  then  cooled  and  a  small  amount  of^  water 
added,  together  with  two  or  three  drops  of  hydrochloric  acid. 
When  all  is  dissolved,  about  30  to  40  drops  of  strong  sulphuric 
acid  is  added,  and  the  whole  again  evaporated  to  dryness  and 
ignited  until  no  more  fumes  appeaiy  and  finally  brought  to  a 
full  red  heat.  It  is  absolutely  necessary  at  this  point  that  fumes 
do  appear,  otherwise  it  will  be  necessary  to  again  add  water  with 
a  few  drops  more  sulphuric  acid,  evaporate,  and  ignite. 

The  residue  -in  the  dish  now  consists  of  the  lime  and  magnesia 
present  in  the  portion  of  the  sample  taken  (with  possibly  some- 
times traces  of  soda  and  potash,  which  may  be  here  disregarded), 
now  in  the  form  of  anhydrous  sulphates.  The  residue  here 
obtained  should  be  of  a  pure  white  color.  It  is  cooled  in  a  desic- 
cator and  weighed  as  rapidly  as  possible,  as,  if  there  is  much 
sulphate  of  magnesia  present,  it  will  rapidly  absorb  moisture  from 
the  air  and  gain  in  weight.  Deducting  the  weight  of  the  dish 
leaves  the  combined  weights  of  the  sulphate  of  lime  and  sulphate 
of  magnesia,  which  can  be  formed  from  the  amount  of  the  sample 
taken  for  this  estimation,  0.5  grammes. 

After  weighing,  the  substance  in  the  dish  is  transferred  by  the 
aid  of  a  little  water  from  the  washing-bottle  to  a  small  beaker. 
Any  adhering  particles  may  be  removed  by  rubbing  with  the  clean 
tip  of  the  finger,  and  should  afterward  be  rinsed  into  the 
beaker.  Any  lumps  should  be  broken  down  with  the  end  of  a 
glass  rod.  Two  or  three  drops  of  hydrochloric  acid  are  next 
added  and  the  solution  well  stirred.  An  undissolved  portion  will 
almost  always  remain.  Next  about  two  drops  of  sulphuric  acid 
are  added  and  stirred.  Strong  alcohol  is  next  added  equal  in 
bulk  to  about  twice  the  volume  of  the  liquid  in  the  beaker,  the 
whole  well  stirred  and  allowed  to  stand,  with  occasional  stirring, 


MAGNESIA.  365 


for  two  hours  or  more.  It  is  then  to  be  filtered  and  the  filter 
washed  two  or  three  times  with  a  mixture  of  two  volumes  of 
strong  alcohol  and  one  volume  of  water.  It  is  then  washed  with 
a  mixture  of  equal  volumes  of  alcohol  and  water  as  long  as  the 
washing  continues  to  remove  anything,  which  may  be  ascertained 
by  allowing  a  drop  or  two  to  fall  from  the  funnel  on  a  clean 
watch-glass  and  then  evaporating  it  by  gently  moving  the  glass. 
If  no  appreciable  residue  is  left  on  the  glass,  the  washing  may  be 
considered  finished.  We  now  have  oil  the  filter  all  the  lime  as 
sulphate  of  lime,  and  all  the  magnesia  in  the  solution.  It  only 
remains,  then,  to  dry  and  ignite  the  precipitate  of  sulphate  of 
lime  and  calculate  the  lime  m  it. 

Sulphate  of  Lime  (CaSO4)  x  0.4118  =  Lime  (CaO). 

We  next  subtract  the  actual  sulphate  of  lime,  weighed  as  above, 
from  the  weight  of  the  mixed  sulphates  of  lime  and  magnesia 
found  previously,  the  difference  being  sulphate  of  magnesia,  which 
multiplied  by  0.3333  =  magnesia,  MgO. 

A  good  lime  for  building  purposes  or  for  causticising  should  be 
almost  entirely  free  from  magnesia.  For  the  best  results  in  mak- 
ing sulphite  liquor  it  should  carry  at  least  35  per  cent,  of  mag- 
nesia. ,f 

Magnesium  Hydrate. 
Symbol,  MgH2O2- 

Magnesia. 
Symbol,  MgO  —  Valency,  II.  5-  Molecular  weight,.  40. 

The  remarks  above,  in  regard  to  calcium  hydrate  and  lime,  at 
the  beginning  of  the  last  section,  apply  equally  to  magnesium 
hydrate  and  magnesia. 

Magnesia  is  recognized  in  solution  by  means  of  solution  of 
phosphate  of  soda.  The  solution  to  be  tested  must  contain  no 
metallic  salts  other  than  those  of  iron  and  alumina.  Some  am- 
monium chloride  is  first  added  to  the  solution,  then  ammonia  in 
excess,  the  liquid  boiled  and  filtered  from  the  alumina  and  sesqui- 
oxide  of  iron  precipitated.  Oxalate  of  ammonia?  is  added  to  the 
filtrate  in  considerable  amount,  and  if  a  precipitate  appears,  the 
liquid  is  heated  in  a  water-bath,  and  again  filtered.  More  ammonia 


366  THE  VffSMISTXY  OF  PAPER-MAKING. 


is  added  to  the  filtrate,  and  some  phosphate  of  soda  solution,  and 
the  liquid  well  stirred  with  a  glass  rod,  allowirg  the  rod  to  rub 
the  sides  and  bottom  of  the  glass.  If  magnesia  is  present,  a  pre- 
cipitate soon  appears  as  a  fine,  white  crystalline  powder,  which 
soon  settles,  leaving  the  liquid  clear*  If  very  little  MgO  is  pres- 
ent, it  may  appear  only  after  a  little  time,  and  then  only  as  white 
streaks  at  tiiose  places  where  the  rod  has  marked  the  glass  in 
stirring.  If  metallic  salts  are  present,  the  slightly  acid  solution 
must  first  be  treated  with  sulphuretted  hydrogen  gas,  by  bubbling 
the  gas  through  the  solution  until  it  smells  strongly  of  the  gas 
after  shaking.  It  is  then  to  be  filtered,  and  to  the  filtrate  some 
ammonia  is  added,  and  then  ammonium  sulphide  as  long  as  the 
latter  causes  a  precipitate.  The  liquid  is  again  filtered,  and  an 
excess  of  oxalate  of  ammonia  is  added,  to  separate  lime  present. 
After  warming  for  some  time,  the  liquid  is  filtered  from  the  lime 
precipitate,  tind  is  then  ready,  after  cooling,  to  be  tested  for  mag- 
nesia with  phosphate  of  soda,  after  the  manner  first  described. 

Quantitative.  —  Magnesia  is  estimated  by  weighing  it  as  mag- 
nesium pyrophosphate,  Mg2P2Or  This  substance  multiplied  by 
0.8604  gives  the  equivalent  weight  of  magnesia,  MgO. 

The  solution  in  which  MgO  is  to  be  determined  must  be  freed 
from  all  other  substances  except  soda  and  potash  and  ammonia, 
as  described  above.  To  the  solution  thus  prepared  a  large  excess 
of  ammonia  is  added,  and  phosphate  of  soda  solution  in  excess, 
The  liquid  is  well  stirred,  taking  care,  in  this  case,  to  avoid  touch- 
ing the  sides  and  bottom  of  the  glass  with  the  rod,  since  this 
will  cause  the  precipitate  to  adhere  to  the  glass.  The  beaker  is 
then  covered,  and  allowed  to  rest  for  at  least  two  hours.  It 
is  then  filtered,  and  the  precipitate  rinsed  on  to  the  filter  by  the 
aid  of  a  wash-bottle  filled  with  water  8|-  parts,  and  ammonia, 
strong,  1^  parts.  It  is  necessary  to  employ  this  dilute  ammonia 
for  washing,  instead  of  water,  as  the  latter  would  dissolve  the 
precipitate.  The  precipitate  should  be  washed  until  a  drop  of 
the  washings,  to  which  a  drop  of  nitric  acid  has  been  added,  gives 
no  cloud  on  the  addition  to  it  of  a  drop  of  a  solution  of  silver 
nitrate.  After  the  precipitate  is  thoroughly  washed,  it  is  dried, 
and  transferred,  as  carefully  as  may  be,  to  a  small  crucible  (plat- 
inum by  preference,  though  porcelain  will  answer),  and  ignited 
to  a  full  red  heat,  The  filter,  with  the  remainder  of  the  precipi- 
tate adhering,  is  then  thrown  into  the  crucible  and  ignited,  until 


CARBONATES.  367 

the  carbon  of  the  filter  is  entirely  consunted,  and  the  whole  of  a 
bright  red  heat.  It  is  then  cooled  and  weighed  ;  and  the  weight 
of  the  precipitate  multiplied  by  0.3604  gives  the  actual  weight  of 
MgO  in  the  portion,  of  the  sample  operated  on. 

CARBONATES 
COMPOUNDS  OF  BASIC  (ALKALINE)  OXIDES  WITH  CARBONIC  AClD. 

Those  which  are  soluble  in  water,  carbonates  of  soda,  potash, 
and  ammonia,  give  solutions  which  show  an  alkaline  reaction  with 
litmus.  AH  are  decomposed  by  acids  in  general  with  liberation  of 
carbonic  acid  gas  and  formation  of  that  salt  of  the  base  correspond- 
ing to  the  acid  employed. 

SODIUM   CARBONATE. 

Sal  Soda  —  Soda  Crystals  (Washing  Soda)  —  Soda-Ash. 

For  specific  gravity  of  solutions  and  per  cent,  of  -the  salt  contained  see  Appendix. 
Soda  crystals,  or  washing  soda,  is  crystallized  carbonate  of  soda. 
Symbol,  Na2CO,,  10  aq,  —  Valency,  II.  —  Molecular  weight,  286. 

Carbonates  of  soda,  potash,  and  ammonia  all  agree  in  being  solu- 
ble in  water;  their  solutions  effervesce  on  the  addition  of  an  acid, 
and  all  give  a  white  precipitate  with  solution  of  calcium,  chloride. 
Solution  of  ammonium  carbonate  is,  however,  distinguished  from 
the  other  two  by  the  strong  smell  of  ammonia  developed  on  the 
addition  of  caustic  soda  solution  and  warming.  Carbonates  of 
soda  and  potash  are  distinguished  by  the  flame  reaction  (see  under 
Caustic  Potash),  best  applied  after  adding  a  slight  excess  of  hydro- 
chloric acid.  . 

Soda-Ash. 
Symbol,  N^CO;,.  —  Valency,  II.  —  Molecular  weight,  10ft. 


Soda-ash  (Solvay)  is  nearly  pure  and  nearly  anhydrous  ciu-bonate 
of  soda.  Soda-ash  may  be  formed  from  soda  crystals  by  furnacing, 
which  in  this  case  serves  simply  to  drive  off,  or  dry  out,  the 
combined  water,  10  aq.,  of  the  crystals  ;  conversely,  soda  crystals 
are  made  from  ash  by  simply  dissolving  and  allowing  to  crystallize. 

The  amount  of  "alkali,"  Na2O,  in  soda-ash  or  crystals  may  be 
estimated  by  titration  with  standard  acid* 


368  THE  CHEMISTRY  OF  PAPER-MAKING. 

The  proper  amount  to  be  weighed  out  for  this  purpose  so  that 
the  number  of  normal  cubic  centimetres  of  acid  consumed  shall 
read  per  cents,  of  alkali  direct  is  31  grammes.  This  is  to  be  dis- 
solved, and  the  solution  made  to  1000  c.c.  100  c.c.  of  this  solu- 
tion are  to  be  filtered  through  a  dry  (wet  with  the  solution,  and 
not  with  water)  filter  and  titrated,  the  solution  being  colored  with 
litmus  solution,  as  under  Caustic  Soda  (which  see),  the  only  addi- 
tional precaution  being  to  continue  the  boiling  after  the  addition 
of  acid  sufficiently  long  to  make  sure  that  a  red  color  has  been 
obtained,  which  will  not  turn  to  blue  or  violet  on  longer  boiling. 

The  percentage  of  carbonate  of  soda  may  be  calculated  to 
that  of  alkali  by  the  proportion 


62   :   106  9  %  NaoO  found  :  x, 

and  the  percentage  of  soda  crystals  equivalent  to  the  alkali  found 
by  the  proportion 

Na2O     Na,CO3  10  aq. 

62    :       286       =  %  NaaO  found  :  x. 


The  soda-ash  of  the  market  is  classified  as  carbonated  or  caustic 
ash,  according  as  all  the  alkali  in  it  exists  as  carbonate,  or  part  as 
carbonate  and  part  as  caustic  soda.  The  testing  of  carbonated 
ash  for  technical  uses  is  commonly  limited  to  the  determination 
of  the  total  alkali,  NagO,  it  contains.  Sometimes*  however,  in 
old  process  or  "  Leblanc  "  ash  an  estimation  of  the  sulphate  of 
soda  may  be  useful,  since  for  use  in  the  manufacture  of  "soda 
pulp  "  a  small  percentage  of  sulphate  of  soda  in  the  ash  purchased 
is  rather  an  advantage  than  otherwise. 

The  percentage  of  sulphate  of  soda  present  is  easily  calculated 
from  the  percentage  of  sulphuric  anhydride*  SO3,  contained. 

This  latter  is  determined  as  follows  :  — 

100  c.c.  of  the  solution  prepared  for  titration,  filtered  as  before 
through  a  dry  filter,  are  transferred  to  a  beaker,  and  hydrochloric 
acid  cautiously  added  as  long  as  each  addition  produces  effer- 
vescence. A  few  drops  more  are  added  to  render  the  solution 
strongly  acid,  and  the  solution  covered  with  a  glass  and  heated 
to  boiling.  Barium  chloride  solution  is  then  added  so  long  as  it 
produces  a  precipitate,  and  the  whole  allowed  to  stand  in  a  warm 
place  until  the  precipitate  has  settled  and  the  solution  above  it 


CARBONATES.  369 


become  clear.  The  solution  is  then  poured  carefully  on  to  a  filter, 
taking  care  to  disturb  the  precipitate  as  little  as  possible  while 
pouring  out  the  liquid.  After  all  the  liquid  has  passed  through 
the  filter,  the  precipitate  is  transferred  to  the  filter  by  the  aid  of 
a  wash-bottle  filled  with  hot  water,  and  the  filter  precipitate  thor- 
oughly washed  with  the  water.  It  is  then  dried,  transferred  to  the 
platinum  crucible,  the  filter  carefully  folded  and  added,  and  the 
whole  strongly  ignited.  The  weight  of  the  ignited  barium  sul- 
phate, BaSO4,  multiplied  by  0.3433,  equals  sulphuric  anhydride, 
SO3,  which  may  then  be  calculated  into  per  cents,  of  the  original 
ash. 

The  equivalent  sulphate  of  soda  may  be  found  by  the  proportion 


S03 

80  :  142  =  %  of  S03:  x  %  of  NagS04,  sulphate  of  soda, 

and  the  percentage  of  alkali,  Na2O,  which  it  can  furnish  on  con- 
version by  the  proportion 


Na2O 

142    :  62  =  %  sulphate  of  soda:  a;  (%  of  equivalent-  alkali-). 


Caustic  Ash. 

The  total  alkali,  Na2O,  in  caustic  ash  and  the  sulphate  present 
are  to  be  estimated  exactly  as  in  carbonated  ash  just  described. 
In  addition  to  these  determinations,  however,  a  knowledge  of  the 
actual  caustic  alkali  present  is  necessary  to  fix  upon  the  value  of 
the  ash.  This  is  determined  as  follows. 

250  c.c.  of  the  solution  prepared  for  titration  of  the  total  alkali 
is  transferred  to  a  500  c.c.  flask,  and  the  small  flask  well  rinsed 
into  the  larger,  using  as  little  water  as  practicable  for  the  purpose. 
A  strong  solution  of  barium  chloride  is  then  added,  with  shaking 
so  long  as  it  produces  a  precipitate.  A  little  more  of  the  barium 
chloride  is  added,  and  the  flask  filled  to  the  mark  with  water  and 
well  shaken. 

The  flask  is  corked  and  allowed  to  rest  until  the  white  precipi- 
tate has  settled  and  the  solution  above  has  become  clear.  100  c*c. 
of  this  solution  are  then  filtered  through  a  dry  filter,  the  funnel 
being  kept  covered  with  a  glass  during  the  filtration.  This 
solution  (100  c.c.)  is  then  transferred  to  a  beaker  or  dish,  and 
litmus  added  and  titrated  with  standard  acid. 


370  TEE  CB&MISTRY  OF  PAPER-MAKING. 

It  is  not  necessary  to  heat  the  solution  during  this  titration. 
The  number  of  normal  cubic  centimetres  of  acid  employed  multi- 
plied by  two,  since  the  100  c.c.  of  the  last  solution  is  equal  to  only 
50  c.c.  of  the  original  solution  prepared,  gives  the  percentage  of 
alkali,  Na2O,  existing  as  caustic  soda,  NaHO,  in  the  sample. 

Black  Ash. 

This  is  a  soda-ash  containing  a  greater  or  less  amount  of  finely 
divided  carbon,  from  which  it  derives  its  black  or  dark  gray  color. 
It  also  contains  ordinarily  small  amounts  of  sulphide  of  soda, 
which  is  formed  from  any  sulphate  which  may  have  been  present 
before  furnacing  the  latter,  being  reduced  by  the  carbon  or  organic 
matter  at  the  high  temperature  of  the  furnace. 

The  valuation  of  black  ash  for  technical  purposes  is,  in  most 
cases,  limited  to  a  determination  of  its  total  alkaline  strength  by 
titration,  as  under  Soda-ash,  above.  This  would  include  the  alkali, 
N^O,  present  as  sulphide  as  well  as  that  present  as  actual  car- 
bonate. In  testing  a  well-burned  black  ash  no  variation  will  be 
found  to  be  necessary  from  the  method  given  above  for  the  titra- 
tion of  soda-ash,  as  the  100  c.c.  of  liquor  filtered  out  for  the 
test  will  be  found  to  be  practically  colorless.  If,  however,  the 
sample  of  black  ash  has  not  been  thoroughly  burned,  the  filtered 
solution  may  be  quite  dark,  or  even  black,  in  color  from  partially 
carbonized  matter  dissolved. 

In  this  case,  the  simplest  way  out  of  the  difficulty,  perhaps,  is 
to  throw  away  the  solution  already  prepared,  and  weigh  out  a 
new  lot  of  31  grammes.  This  is  then  transferred  to  a  platinum 
dish  (best  to  the  evaporating-dish)  and  thoroughly  ignited  over 
the  lamp.  The  whole  is  then  transferred  tp  the  litre  flask,  the 
dish  well  rinsed  in,  and  after  the  ash  is  dissolved  made  to  the 
mark  as  before.  If  the  Ignition  has  been  well  performed,  a  suf- 
ficiently colorless  solution  will  be  obtained  on  filtering.  The  com* 
plete  analysis  of  black  ash  is  a  problem  of  so  complicated  a  nature 
as  to  be  best  performed  by  the  professional  chemist.  Not  infre- 
quently, however,  such  an  analysis  may  serve  to  point  out  an 
erroneous  method  of  practice,  or  an  avoidable  waste  in  the  manu- 
facture, of  which  this  black  ash  is  a  bye-product. 


CARBONATES.  871 


Bicarbonate  of  Soda  (Baking-Soda). 
Symbol,  NaHCO*.  —  Valency,  I.  —Molecular  weight,  84. 

This  salt  is  much  less  soluble  in  water  than  the  carbonate  of 
soda.  Its  reactions  in  general  are  similar  to  those  of  the  neutral 
carbonate,  but  less  strong. 

It  contains  about  one-half  as  much  alkali,  Na2O,  as  the  simple 
carbonate*  and  about  twice  as  much  carbonic  acid.  On  this 
account,  and  on  account  of  its  being  very  mildly  alkaline,  it  is 
always  employed  in  all  baking-powders  as  the  source  of  the  gas 
required  to  "  raise  "  the  bread. 

The  testing  of  bicarbonate  of  soda  requires  a  determination  of 
the  total  alkali,  Na2O,  and  also  a  determination  of  the  total 
carbonic  anhydride,  CO2  (commonly  called  carbonic  acid),  present. 
From  the  data  furnished  by  the  two  determinations,  the  actual 
amounts  of  bicarbonate  and  of  carbonate  of  soda  present  may  be 
calculated.  Bicarbonate  made  by  the  "  Solvay  Process "  also 
contains  a  small  percentage  of  ammonia  in  combination  with 
carbonic  acid.  When  present,  ammonia  must  also  be  determined. 

The  total  alkali  in  bicarbonate,  free  from  ammonia,  may  be 
determined  by  titration  with  standard  acid. 

8.100  grammes  of  the  substance  are  to  be  weighed,  transferred 
to  a  beaker  or  dish  with  about  100  c.c.  of  water,  litmus  added, 
and  titrated  direct  with  acid,  care  being  taken  to  thoroughly  boil 
the  solution  during  the  titration.  The  number  of  normal  cubic 
centimetres  of  acid  used  gives  the  per  cents,  of  alkali,  Na2O, 
present. 

When  ammonia  is  present,  the  sample  weighed  out  for  the  titra- 
tion must  be  ignited  for  some  time  at  a  moderate  heat,  which  will 
expel  all  the  ammonia,  before  dissolving  it  for  titration. 

The  estimation  of  carbonic  acid  is  conducted  in  a  special  form 
of  apparatus,  called  the  "Schrpetter  Carbonic  Acid  Apparatus." 
The  use  of  this  apparatus  is  as  follows :  The  apparatus  being  clean 
and  dry,  2  grammes  to  5  grammes  of  the  substance  to  be  examined 
is  weighed  and  transferred  very  carefully  to  the  small  flask  forming 
the  base  of  the  apparatus.  About  10  c.c.  of  water  is  then  added 
and  the  cork  carefully  inserted.  The  stopcock  between  the 
flask  and  the  bulb-tube  directly  above  it  is  closed,  and  the  bulb 
wi£h  hydrochloric  or  nitric  acid,  the  neck  carefully  wiped, 


372  THE  CHEMISTRY  OF  PAPER-MAKING. 

and  its  stopper  inserted.  The  other  large  bulb  is  next  tilled  about 
one-half  full  of  strong  sulphuric  acid,  the  neck  wiped,  and  the 
stopper  inserted.  The  whole  apparatus  with  its  contents  is  now 
weighed  carefully  and  the  weight  recorded.  The  cock  is  next 
opened  slightly  so  as  to  allow  the  acid  in  the  bulb  to  very  slowly 
drip  into  the  flask.  This  at  once  frees  carbonic  acid  gas  from  the 
carbonate  there  contained,  which  is  forced  to  bubble  through  the 
bulb  containing  sulphuric  acid.  This  acid  serves  to  remove  and 
retain  all  moisture  which  may  be  carried  up  by  the  gas,  so  that  only 
pure,  dry  CO2  gas  finally  escapes  from  the  apparatus.  After 
making  certain  that  sufficient  acid  has  been  allowed  to  enter  the 
flask  to  decompose  the  whole  of  the  carbonate  present,  the  cock  is 
olosed,  and  the  contents  of  the  flask  heated  cautiously  to  boiling 
and  allowed  to  boil  until  steain  commences  to  be  driven  over  into 
the  bulb  containing  the  sulphuric  acid.  It  is  then  removed  from 
the  heat  and  the  cock  at  once  opened  to  allow  the  remaining  acid 
to  run  in  or  air  to  be  drawn  into  the  flask  as  the  steain  condenses 
and  the  apparatus  allowed  to  become  cold.  It  is  then  once  more 
weighed,  and  this  weight  deducted  from  the  previous  weight  leaves 
the  loss  of  weight  during  the  operation,  which,  if  sufficient  care  has 
been  employed,  represents  the  weight  of  carbonic  anhydride,  CO2, 
in  the  amount  of  substance  operated  upon.  This  weight  may  be 
easily  figured  into  per  cents. 

The  method  of  procedure  described  above  may  serve  for  the 
estimation  of  carbonic  acid,  CO2,  in  any  carbonate.  The  ammonia 
present  in  Solvay  bicarbonate  may  be  determined  by  placing  a 
weighed  amount,  say  about  tvpo  or  three  grammes,  of  the  bicar- 
bonate in  a  tube  of  hard  glass  about  six  inches  in  length  and  a 
half-inch  in  diameter,  known  as  an  ignition  tube.  A  loose  plug 
of  asbestos  is  placed  near  the  mouth  of  the  tube,  which  is  fitted 
with  a  good  cork.  This  in  turn  carries  a  piece  of  glass  tube, 
passing  just  through  the  cork  into  the  combustion  tube,  and  bent 
downward  in  front  of  the  tube,  so  as  to  pass  through  a  cork  fitted 
into  one  end  of  a  U-tube.  Two  or  three  cubic  centimetres  of 
standard  acid,  accurately  measured  from  a  burette,  are  placed  in 
the  U-tabe  and  colored  with  litmus.  Enough  water  should  be 
added  so  that  the  liquid  in  the  tube  may  well  cover  the  bend 
of  the  tube.  The  ignition  tube  should  be  held  by  a  clasp  in  a 
nearly  horizontal  position  and  a  gentle  heat  applied  for  some  time 
to  the  portion  of  the  tube  containing  the  carbonate,  and  gradually 


CARBONATES.  878 


increased  nearly  to  redness.  This  will  expel  all  the  ammonia 
present,  which  will  be  driven  into  the  U-tube,  and  there  absorbed 
by  the  acid  contained  therein. 

When  no  more  bubbles  are  seen  to  pass  through  the  liquid  in 
the  U-tube,  and  the  substance  in  the  ignition  tube  is  very  nearly 
or  quite  red  hot,  the  connection  between  the  two  tubes  may  be 
broken  and  the  lamp  removed. 

The  liquid  should  next  be  transferred  from  the  U-tube  to  a 
beaker,  and  the  tube  carefully  rinsed,  and  the  acid  remaining  in 
the  liquid  unneutralized  titrated  with  standard  soda.  The  number 
of  normal  cubic  centimetres  of  soda  employed,  taken  from  the 
number  of  normal  cubic  centimetres  of  acid  originally  placed  in 
the  U-tube,  leaves  the  normal  cubic  centimetres  neutralized  by 
the  ammonia  from  the  sample  of  bicarbonate  weighed.  This 
latter  number  multiplied  by  0.017  will  give  the  weight  of 
ammonia,  NH3,  obtained  from  the  sample  operated  on,  and  this 
weight  may  be  readily  calculated  into  equivalent  per  cents. 

If  1.7  grammes  of  the  sample  be  weighed  for : the  experiment, 
the  number  of  normal  cubic  centimetres  of  acid  neutralized  by  the 
ammonia  driven  off  as  above  will  represent  per  cents,  of  NH8  in 
the  sample  analyzed. 

Carbonate  of  Potash  (Pearlask — .Salt  of   Tartar). 
Symbol,  K2OO8  —  Valency,  II.  — Molecular  weight,  138,2. 

This  substance,  though  formerly  much  used  in  the- arts,  is  now 
almost  entirely  discarded  in  favor  of  soda-ash,  which  has  been 
found  to  answer  the  required  purpose  in  a  large  majority  of  cases 
equally  as  well  as  the  potash  salt,  and  to  offer  in  very  many 
instances  many  advantages  over  the  latter,  not  the  least  of  which 
is  its  greater  cheapness. 

The  methods  for  testing  pearlash  «re  precisely  similar  to  those 
given  in  detail  under  Carbonate  of  Soda,  which  see. 

The  proper  amount  of  pearlash  to  be  weighed  out  for  titration 
is  47.1  grammes  to  be  made  to  1000  C.G.,  and  100  c.c.  employed  for 
the  test.  The  normal  cubio  centimetres  used  will  then  represent 
pericents-.  of  potash,  K2O,  present. 


374  THE  CHEMISTRY  OF  PAPER-MAKING. 


CARBONATE   OF  LIME. 

Chalk  (French   White —  Whiting  —  Marble  —  Limestone). 
Symbol,  CaCO3  —Valency,  II. —Molecular  weight,  100. 

Almost  entirely  insoluble  in  pure  water  —  water  containing 
alkaline  salts  and  carbonic  acid  dissolves  it  in  somewhat  largei 
amounts. 

The  test  required  for  chalk,  French  white,  or  whiting,  is  usually 
one  for  purity  alone,  and  consists  in  dissolving  a  portion  in  dilute 
hydrochloric  acid.  A  pure  article  should  be  entirely  dissolvec 
by  the  acid  —  absence  of  sand,  or  silicates  (clay).  The  solutior 
is  next  tested  with  barium  chloride  for  presence  of  sulphates 
A  complete  analysis  of  marble  and  limestone  is  frequently  re 
quired.  This  may  be  performed  with  sufficient  accuracy  for  niosl 
technical  purposes  in  exactly  the  same  way  as  described  for  tin 
the  analysis  of  Lime  above,  which  see. 

The  carbonic  acid,  CO2 ,  may  be  determined  by  the  aid  of  tht 
Schroetter  apparatus,  described  above,  when  desired. 


CARBONATE   OF  MAGNESIA. 

Maynesite. 
Symbol,  MgCO,.  —  Valency,  II.  —Molecular  weight,  84. 

This  substance  is  worth  noting  as  being  the  crude  base  employed 
in  making  the  solution  used  in  the  "  Ekman  Sulphite  Pulp  Pro- 
cess." An  analysis  of  this  substance  for  technical  purposes  may 
be  made  precisely  as  directed  for  the  analysis  of  limestone.  The 
precaution,  however,  must  be  taken  of  weighing  the  ignited  sul- 
phates with  the  dish  containing  them  covered  with  a  glass,  and  the 
weighing  must  be  performed  as  rapidly  as  possible,  since  ignited 
magnesium  sulphate  absorbs  moisture  very  rapidly  from  the  air, 
and  increases  in  weight  in  consequence. 

The  ignition  of  the  sulphates  also  should  not  be  prolonged 
beyond  the  time  necessary  to  expel  all  the  free  sulphuric  acid 
or  the  heat  raised  beyond  a  moderate  red  heat,  since  sulphate 
of  magnesia  is  not  absolutely  unalterable  under  prolonged  and 
intense  ignition. 


SULPHATES.  375 


CARBONATE   OF  ZINC. 

Symbol,  ZnCO3.  —Valency,  II.  —Molecular  weight,  125. 

Impurities  to  be  looked  for :  lead  and  lime  carbonates,  and  sul- 
phate of  lime  and  insoluble  matter. 

The  substance  to  be  examined  should  be  dissolved  in  hydro- 
chloric acid,  in  which,  if  pure,  it  will  be  completely  soluble.  The 
solution  nearly  neutralized  with  carbonate  of  soda,  but  still  dis- 
tinctly acid,  is  treated  with  sulphuretted  hydrogen  by  bubbling 
the  gas  through  for  a  little  time  —  any  blackening  of  the  solution, 
or  the  appearance  of  a  black  precipitate,  indicates  the  presence 
of  lead. 

The  solution,  filtered  if  necessary,  should  then  be  rendered 
ammoniacal,  and  sulphide  of  ammonia  added  (best  to  the  boiling 
solution)  so  long  as  it  continues  to  cause  a  precipitate.  The  solu- 
tion, filtered  from  this  precipitate,  may  be  tested  for  lime  with 
oxalate  of  ammonia  solution,  as  previously  described. 

SULPHATES. 

The  sulphuric  acid  in  sulphates  is  always  determined  in  the 
same  way ;  namely,  by  precipitating  it  by  means  of  barium  chlo- 
ride solution  from  the  solution  rendered  acid  by  hydrochloric  acid, 
and.  weighing  the  barium  sulphate  produced. 

For  the  details  of  the  manipulation,  see  estimation  of  sulphate 
of  soda  in  Soda-Ash. 

AtUM. 

Potash  Alum,  K2A12  4SO4,  24H2O.          —Molecular  weight,  948. 

Soda  Alum,  Na.j  A12  4  SO4,  24  H2O.  "  «        916. 

Ammonia  Alum,          (NH4).,A12 4 SO,,  24H2O.  —          "  "        906. 

Sulphate  of  Alumina,  Ala  3 SO4,  18 H3O.  —         "  "        666. 

Since  the  value  of  all  alums  for  paper-makers'  purposes  depends 
on  the  amount  of  combined  alumina  they  contain,  and  on  the 
absence  of  free  acid,  of  iron  and  of  insoluble  matter,  it  becomes 
necessary  for  our  present  purpose  to  give  methods  for  the  deter- 
mination of  these  four  things  only. 

Tfye  presence  or  absence  of  iron  may  be  determined  by  the  use 
of  ferrocyanide  of  potash.  For  this  purpose  a  considerable 


376  THE  CHEMISTRY  OF  PAPER-MAKING. 

amount  of  alum  should  be  dissolved  in  a  moderate  quantity  of 
water,  and  the  solution  heated  to  boiling  after  the  addition  of  a 
few  drops  only  of  nitric  acid.  The?  solution  is  then  allowed  to 
cool,  and  some  freshly  made  solution  of  ferrocyanide  of  potash 
(yellow  prussiate)  added.  If  iron  is  present,  a  blue  color  will  be 
developed  of  greater  or  less  depth,  according  as  there  is  more  or 
less  iron  present.  If  no  iron  is  present,  the  solution  will  remain 
colorless. 

Many  methods  have  been  proposed  for  testing  an  alum  directly 
for  the  presence  of  free  acid,  but  in  our  hands  none  have  proved 
entirely  satisfactory. 

For  the  valuation  of  an  alum,  then,  we  may  proceed  as  follows : 
Weigh  out  25  grammes  and  dissolve  in  about  200  c.c.  of  warm 
water.  When  all  is  dissolved,  filter  from  any  insoluble  matter 
into  a  500  c.c.  measuring-flask  and  wash  the  residue  on  the  filter 
thoroughly  with  hof  water.  This  residue  dried,  ignited,  and 
weighed,  gives  the  insoluble  matter  in  the  25  grammes  taken. 

The  filtered  solution  is  next  made  (after  cooling)  to  500  c.c.  and 
well  mixed.  100  c.c.  of  this  solution,  equivalent  to  5  grammes 
of  the  alum,  are  again  made  to  500  c.c.  (solution  No.  2). 

100  c.c.  of  the  latter  (solution  No.  2),  equivalent  to  1  gramme 
of  the  alum,  is  taken  for  the  estimation  of  total  sulphuric  acid 
present  by  precipitation  with  barium  chloride  (see  Sulphate  in 
So  da- Ash). 

100  c.c.  of  solution  No.  2  is  also  taken  for  the  determination 
of  alumina.  This  is  diluted  to  about  400  c.c.  in  a  beaker,  and 
some  ammonia  chloride  solution  added.  It  is  then  heated  nearly 
to  boiling  and  ammonia  solution  added,  drop  by  drop,  until  the 
smell  of  ammonia  can  just  be  distinctly  detected  in  the  solution. 
It  is  then  heated  to  just  below  the  boiling-point  for  some  time, 
until  the  odor  of  ammonia  can  no  longer  be  detected  in  the  solu- 
tion. The  volume  of  the  solution  should  be  kept  nearly  the  same 
by  the  addition  of  hot  water  from  time  to  time  as  the  solution 
evaporates.  This  treatment  precipitates  all  the  alumina  as  well 
as  all  the  sesquioxide  of  iron  present  in  the  form  of  the  hydrated 
sesquioxides  of  alumina  and  of  iron,  a  very  bulky,  gelatinous  pre- 
cipitate, white  if  no  iron  is  present,  but  more  or  less  colored  if 
iron  is  present.  The  precipitate  should  be  allowed  to  settle  and 
the  clear  liquor  carefully  decanted  through  a  good-sized  filter. 
Water  is  added  to  the  precipitate  in  the  beaker  and  brought  to  a 


SULPHATES.  377 


boil.  It  is  again  allowed  to  settle,  and  decanted  through  the 
same  niter  as  before.  The  boiling  up  with  water  and  decanting  is 
best  repeated  a  second  time,  and  finally  the  precipitate  is  trans- 
ferred to  the  filter  and  washed  .thereon  with  hot  water  until  a 
drop  of  the  washings  gives  at  most  only  a  very  slight  cloud  when 
tested  on  a  glass  with  a  drop  of  silver  nitrate  solution* 

The  precipitate  is  then  dried  thoroughly  in  the  water  oven, 
separated  as  completely  as  possible  from  the  filter,  and  ignited  in 
a  platinum  crucible  tightly  covered.  Oare  must  be  taken  to  have 
the  precipitate  thoroughly  dry  before  igniting,  and  to  keep  the 
crucible  tightly  covered  until  the  substance  is  raised  to  a  full  red 
heat.  The  crucible  is  then  allowed  to  cool,  and  the  filter  added, 
folded  up,  and  again  ignited  —  first  with  the  covor  on  until  all 
inflammable  vapors  cease  to  appear,  and  then  with  access  of  air 
until  the  carbon  of  the  filter  is  entirely  consumed.  It  is  then 
cooled  in  the  desiccator  and  weighed  covered.  The  weight  of  the 
precipitate  gives  the  weight  of  the  alumina,  A12O3,  and  sesqui- 
oxide  of  iron,  Fe2O8,  in  1  gramme  of  the  sample. 

To  obtain  the  amount  of  alumina,  the  iron  oxide  must  be  sepa- 
rately determined,  and  its  amount  deducted  from  the  total  weight 
of  precipitate,  A12O3  4-  Fe2O8 ,  as  found  above. 

To  find  the  amount  of  iron  oxide  present,  we  may  take  100  c»c. 
of  the  original  solution  above,  equal  to  5  grammes  of  the  sample. 
This  is  transferred  to  a  flask  holding  200  or  300  c.c.,  and  fitted 
with  what  is  known  as  a  Bunsen  or  Krooning  valve.  This  con- 
sists merely  of  a  rubber  stopper  for  the  neck  of  the  flask,  through 
the  centre  of  which  is  slipped  a  short  piece  of  glass  tubing  extend- 
ing just  through  the  stopper  below  and  about  one  inch  above  the 
stopper. 

To  the  upper  end  is  fitted  a  short  piece  of  rubber  tube  about 
an  inch  in  length,  which  has  had  a  short  slit  cut  in  one  side  with 
a  sharp  knife,  the  upper  end  of  the  rubber  tube  being  stopped 
with  a  bit  of  glass  rod.  This  valve  will  open  to  relieve  a  pressure 
from  within  the  flask,  but  will  not  admit  air  into  the  flask.  Some 
pieces  of  pure  iron^free  zinc  are  added  to  the  solution  in  the  flask, 
and  enough  sulphuric  acid  to  cause  a  moderately  rapid  evolution 
of  gas. 

The  stopper  fitted  with  the  valve  as  above  is  then  inserted,  and 
the  whole  allowed  to  rest  for  an  hour  or  two,  taking  care  to  keep 
up  the  evolution  of  gas  during  the  time  by  the  addition  of  ainc 


37S  THE  CHEMISTRY  OF  PAPER-MAKING. 

or  acid  as  may  be  needed.  The  solution  is  then  transferred  to  a 
large  beaker  and  the  flask  rinsed  in*  taking  care  not  to  leave 
any  undissolved  bits  of  zinc  behind. 

A  solution  of  permanganate  of  potash  is  then  dropped  in  from 
a  burette  drop  by  drop,  with  constant  stirring,  until  a  faint  pink 
tint  remains  in  the  solution.  The  number  of  cubic  centimetres  of 
permanganate  solution  used  is  then  read  off,  and  the  equivalent 
amount  -of  sesquioxide  of  iron,  Fe2O3,  ascertained  by  multiplying 
by  the  appropriate  factor. 

The  permanganate  solution  is  made  of  appropriate  strength  by 
weighing  about  3  grammes  of  the  crystallized  permanganate  of 
potash  and  dissolving  in  water  to  make  1000  c.c. 

To  obtain  the  value  of  this  solution  in  terms  of  iron,  Fe,  we 
may  dissolve  about  0.200  grammes  of  fine  piano  wire  by  warming 
with  a  mixture  of  3  volumes  of  water  and  1  volume  of  sulphuric 
acid  in  a  small  flask  fitted  with  a  Krooning  valve,  as  described 
above. 

When  all  is  dissolved  except  some  bits  of  carbon,  the  whole  is 
transferred  '«to  a  large  beaker  with  500  to  600  c.c.  of  water  and 
titrated  with  the  permanganate  solution  as  above,  until  a  pink  color 
remains.  Piano  wire  we  may  take  as  containing  99.7  per  cent. 
of  iron,  Fe;  Then,  if  we  have  dissolved  0.200  grammes,  we  shall 
in  reality  have  a  solution  of  (0.200x0.997  =  0.1994)  0.1994 
grammes  of  iron.  Suppose  this  to  have  consumed,  or  decolorized, 
20  c.c.  of  permanganate  solution.  Then  1  c.c.  of  permanganate 

0  1^94 
will  be  equivalent  to  -^—  -  —  =  0.00997  grammes  of  iron,  Fe,  or 

0.014243  grammes  of  Fe2O3. 


2Fc      Fe2O8  Fe 

112  :  160.  =  0.00997  :  0.014243. 

The  value  of  the  permanganate  solution  must  be  determined  each 
time  directly  before  using,  as  it  is  apt  to  lose  strength  by  keeping, 
with  the  formation  of  a  brown  precipitate.  The  solution  of  iron 
should  always  be  tested  before  titrating  by  amoving  a  small  drop 
from  the  flask  by  means  of  a  rod  and  bringing  it  in  contact  with  a 
drop  of  a  solution  of  potassium  sulphocyanide,  placed  on  a  white 
surface,  as  a  porcelain  dish.  If  any  reddish  color  appears  at  once, 
the  iron  has  not  all  been  dissolved  to  proto-sulphate,  as  is  necessary 
before  it  can  be  titrated.  The  remedy  is  simply  to  allow  it  to 


SULPHATES.  379 


remain  longer  in  contact  with  zinc  in  the  act  of  evolving  hydro- 
gen. When  the  reduction  from  the  ferric  to  the  ferrous  condition 
is  complete,  the  solution  will  give  no  red  color  with  sulphocyanide 
solution.  Certain  "patent"  or  " concentrated  "  alums  are  met 
with,  which  contain  a  small  percentage  of  zinc  sulphate.  This 
is  formed  from  the  use,  at  a  certain  stage  of  the  manufacture, 
of  zinc  for  the  double  purpose  of  neutralizing  free  acid  and  of 
rendering  the  alum  more  porous  and  consequently  more  easily 
dissolved. 

A  qualitative  test  for  the  presence  of  zinc  may  be  made  by 
adding  an  excess  of  ammonia  solution  to  a  moderately  concentrated 
solution  of  the  alum,  heating  to  boiling  and  filtering  from  the 
alumina  (and  iron  oxide)  precipitated.  The  clear  filtrate  is-  then 
heated  to  boiling  and  a  little  ammonia  sulphide  solution  added. 
If  zinc  is  present,  it  will  appear  as  a  white  flocculent  precipitate, 
which  on  boiling  for  a  few  moments  will  readily  settle. 

When  zinc  is  present  in  an  alum,  the  iron  may  be  determined  as 
above ;  but  for  the  estimation  of  alumina  we  must  precipitate  it 
along  with  the  iron  present  as  basic  acetate  of  the  sesquioxide, 
instead  of  the  hydrate  as  in  the  former  case. 

To  this  end  the  solution  must  be  largely  diluted —about  1 
gramme  of  alum  in  500  c.c.  is  proper.  To  the  solution  about  2 
grammes  of  acetate  of  soda  are  added,  and  a  few  drops  of  acetic 
acid.  The  solution  is  then  heated  to  boiling  and  kept  in  active 
ebullition  for  ten  to  fifteen  minutes.  By  this  means  all  the 
alumina  and  sesquioxide  of  iron  are  precipitated  as  basic  acetates, 
while  the  zinc  remains  in  solution.  The  precipitate  is  allowed  to 
settle,  and  the  liquid  decanted  through  a  filter  as  rapidly  as 
possible.  The  precipitate  is  boiled  up  with  water  two  or  three 
times,  allowed  to  settle,  and  the  liquid  decanted  each  time ;  and 
finally,  the  precipitate  is  thrown  on  the  filter  and  the  washing  com* 
pleted  with  boiling  water,  best  containing  a  very  little  ammonium 
acetate.  The  filtrate  and  washings  are  to  be  evaporated  to  a 
moderate  volume— say  to  about  200  c.c.;  and  if  any  precipi- 
tate separates  during  the  concentration,  as  will  usually  be  the 
case;  it  is  to  be  filtered  off,  washed,  ignited,  and  weighed  with  the 
main  basic  acetate  precipitate. 

The  alumina  precipitate  is  to  be  dried  and  ignited  as  above, 
and  weighed  as  A12O3  4- Fe2O3.  From  this  weight  the  weight  of 
the  Fe2O8  found  by  titration  with  permanganate  as  above  is  to  be 


880  THE  CHEMISTRY  OF  PAPER-MAKING. 

deducted,  and  the  remainder  will  be  the  alumina  present  in  the 
1  gramme  of  alum  taken. 

The  filtrate  from  the  basic  acetates  of  alumina  and  sesquioxide 
of  iron  is  to  be  neutralized  as  nearly  as  possible  with  ammonia, 
heated  to  boiling,  and  ammonium  sulphide  added  drop  by  drop  so 
long  as  it  continues  to  produce  a  precipitate.  The  boiling  is  to 
be  continued  for  about  fifteen  or  twenty  minutes.  The  zinc  sul- 
phide is  then  allowed  to  settle,  which  it  will  do  very  rapidly. 
The  clear  liquor  should  then  be  tested  with  a  single  drop  of 
ammonium  sulphide.  If  this  produces  no  cloud,  the  liquid  may 
be  filtered  and  the  precipitate  washed  thoroughly  with  hot  water. 

If  the  addition  of  a  drop  of  the  reagent  produces  a  precipitate, 
the  liquid  should  be  again  boiled  and  tested,  and  so  on  until  the 
reagent  fails  to  give  any  further  cloud  in  the  solution. 

The  zinc  sulphide  is  to  be  dried,  removed  as  far  as  possible 
from  the  filter  into  a  porcelain  crucible,  the  filter  added,  and 
ignited  with  free  access  of  air,  gently  at  first,  and  finally  as 
strongly  as  possible,  with  the  addition  now  and  then  of  a  small 
piece  of  ammonium  carbonate.  The  ignition  should  be  continued 
until  on  cooling  and  weighing  two  consecutive  weights  are 
obtained  alike.  The  strong  ignition  changes  the  zinc  sulphide 
into  zinc  oxide,  ZnO,  and  it  is  weighed  as  such. 

In  the  foregoing  we  have  constantly  used  the  word  u  alum,"  but 
2m ve  really  been  describing  the  analysis  or  valuation  of  alum 
cake.  The  methods  for  the  technical  valuation  of  each  is  the 
same,  however,  so  that  a  single  description  may  serve  for  the 
ivhole  class  of  sulphates  commercially  known  as  alums. 

Free  Acid  in  Alum. 

Numerous  methods  have  been  proposed  for  the  determination  of 
free  acid  in  alums,  but  after  giving  them  an  extended  trial  in  our 
laboratory  we  have  failed  to  find  one  which  we  can  accept  as  even 
iairly  accurate.  Where  this  important  point  must  be  determined, 
we  can,  therefore,  only  recommend  a  complete  analysis. 

Sizing  Test. 

One  of  the  most  satisfactory  tests  to  which  an  alum  for  paper- 
makers'  use  can  be  subjected  is  that  which  we  have  worked  out 
and  called  the  "  sizing  test,"  by  which  the  actual  amount  of  rosin 


SULPHATES.  381 


size  which  a  given  amount  of  alum  will  precipitate  is  determined. 
This  is  effected  as  follows. 

A  standard  size  solution  is  prepared  by  dissolving  about  25 
grammes  of  good  ordinary  rosin  size  in  about  250  c.c.  of  strong 
alcohol.  The  solution  is  then  filtered  from  insoluble  matter, 
and  diluted  with  a  mixture  of  500  c.c.  of  strong  alcohol  and 
300  c.c.  of  water  to  nearly  1000  c.c.  A  little  phenolphtalein 
solution  is  then  added,  and  standard  soda  solution  added  drop 
by  drop*  shaking  after  each  addition  until  a  faint  pink  tinge  is 
observed  in  the  solution.  This  shows  that  all  the  rosin  acids  are 
combined  with  soda,  and  that  the  solution  is  one  of  neutral 
resinate  .of  soda  or  neutral  rosin  size.  The  solution  is  now  to 
be  made  to  1000  c.c.  with  the  diluted  alcohol  mentioned  above, 
and  if  not  entirely  clear,  filtered  again  or  allowed  to  stand  until  it 
settles  clear.  The  clear  alcoholic  solution  constitutes  the  standard 
size  solution. 

The  value  of  this  solution  is  next  to  be  determined,  best  by 
means  of  a  solution  of  pure  crystallized  ammonia  alum,  one  part 
of  which  alum  we  have  found  to  precipitate  2.46  parts  of  neutral 
rosin  size. 

For  this  purpose  the  clear,  colorless  crystals  should  be  coarsely 
crushed  in  a  mortar,  and  the  resulting  powder  pressed  between 
two  sheets  of  filtering  paper  to  remove  any  accidental  moisture. 
Five  grammes  are  then  carefully  weighed  and  dissolved  to  500 
c.c.  Each  cubic  centimetre  of  this  solution  will  then  contain 
0.01  gramme  of  alum. 

TWO  burettes  are  next  filled,  one  with  the  size  solution,  .and  one 
with  the  alum  solution. 

A  flask  of  150  to  200  c.c.  capacity  is  filled  about  two-thirds 
full  of  water,  and  20  c.c.  of  the  size  solution  is  run  into  it 
from  the  burette.  The  alum  solution  is  next  run  in,  a  few  drops 
at  a  time,  the  mouth  of  the  flask  being  closed  with  the  thumb  and 
the  flask  vigorously  shaken  after  each  addition  of  alum,  and  allowed 
to  rest  until  the  flocculent  precipitate  formed  has  risen  clear, 
which  takes  but  a  few  moments.  The  addition  of  the  alum  solu- 
tion should  be  continued  until  the  precipitate  on  rising  leaves 
the  solution  entirely  clear,  without  the  slightest  trace  of  milkiness 
or  opalescence. 

The  number  of  cubic  centimetres  of  alum  xO.Ol  equals  the 
amount  of  ammonia  alum  required  to  precipitate  the  size  in  the 


$82  THE  CHEMISTRY  OF  PAPER-MAKING. 

20  c.e.  of  standard  size  employed.  This  multiplied  by  the  factor 
for  ammonia  aluin,  as  above,  equals  the  quantity  in  grammes  of 
neutral  size  in  20  c.c.  of  the  standard  solution. 

The  actual  test  of  an  alum  is  performed  in  exactly  the  same 
way ;  a  solution  of  5  grammes  of  the  alum  to  500  c.c.  being  em- 
ployed, and,  if  necessary,  filtered  through  a  dry  filter  before  titrat- 
ing. 20  c.c.  of  the  standard  size  solution  are  always  employed, 
and  the  actual  amount  of  neutral  size  it  contains  having  been 
determined  as  above,  it  is  easy  to  calculate  from  the  data  given 
by  the  titration  the  amount  of  size  which  one  part  of  the  alum 
tested  will  precipitate. 

This  test,  as  is  evident,  gives  the  absolute  precipitating  power 
of  the  alum,  and  does  not  discriminate  between  sulphates  of 
alumina,  iron,  or  other  metallic  oxides  which  may  be  present,  or 
free  acid,  all  of  which  have  the  power  of  precipitating  size. 

Moisture  in  Alum. 

One  other  test  as  applied  to  alum  should,  however,  be  noticed 
before  leaving  the  subject,  and  that  is  the  determination  of 
moisture.  This,  in  the  case  of  alums,  cannot  be  determined,  as 
in  most  instances,  by  drying  or  igniting  a  sample,  and  noting  the 
loss  which  it  sustains.  Mere  drying,  even  at  a  temperature  consider- 
ably above  100°  C.,  is  not  sufficient  to  expel  all  the  moisture  from 
an  alum,  while  ignition  drives  off  not  only  the  water,  but  a  portion 
of  the  sulphuric  acid  as  well.  To  determine  the  moisture  in  this 
case,  then,  it  is  necessary  that  we  ignite  the  sample,  best  in  a 
platinum  crucible,  until  fumes  of  SO3  appear  in  abundance ;  then 
cool  and  weigh,  and  note  the  loss.  We  next  treat  the  ignited 
sample  with  hot  hydrochloric  acid,  until  all  lumps  are  broken 
down.  If  the  ignition  has  not  been  too  intense  or  prolonged,  all 
will  dissolve.  It  does  not  matter,  however,  if  all  does  not  dis- 
solve, provided  it  is  well  broken  down,  so  as  to  make  sure  that  all 
soluble  portions  are  brought  into  solution.  The  solution  is  filtered 
and  the  residue  well  washed  on  the  filter  with  hot  water.  The 
filtrate  and  washings  are  next  precipitated  with  barium  chlo- 
ride, and  the  sulphuric  acid  determined.  The  per  cent,  of  SO8, 
here  found,  deducted  from  the  total  SO3  contained  in  the 
sample,  as  determined  above  (see  Sulphate  in  Soda- Ash),  leaves 
tlwi  percentage  of  SO3  driven  off  by  the  ignition.  This  taken 


SULPHATES.  383 


from  the  total  loss  of  weight  by  ignition,  in  per  cents.,  leaves  the 
percentage  of  moisture  in  the  sample. 

Pearl  Hardening  (Crystallised  Sulphate  of  Lime). 
Symbol,  CaSO4,  2  aq.  —  Molecular  weight,  172. 

Pearl  hardening  being  made  ordinarily  by  precipitating  a  soluble 
salt  of  lime  as  calcium  chloride  by  means  of  sulphuric  acid  or. 
sulphate  of  soda,  washing  and  pressing  in  a  filter  press,  the  only 
tests  which  the  substance  calls  for  are  tests  for  free  acids,  for 
chlorides,  and  for  moisture. 

Free  acids  may  be  recognized  by  mixing  a  portion  of  the  sample 
with  water  and  filtering.  If  no  free  acid  is  present,  the  filtered 
solution,  when  tested  with  litmus  solution,  should  show  no  acid 
reaction.  A  portion  of  the  filtered  solution  just  mentioned  may 
be  tested  for  chlorides,  by  adding  a  drop  only  of  nitric  acid  and 
some  nitrate  of  silver  solution.  A  slight  cloud  will  usually  be 
obtained,  as  it  is  difficult  to  remove  all  traces  of  chloride  ;  but  if 
any  considerable  precipitate  forms,  it  will  indicate  that  the  pearl 
hardening  has  been  incompletely  washed. 

Moisture  may  be  determined  by  drying  a  sample  at  100°  C.  in 
the  water-oven  until  it  ceases  to  lose  weight.  The  total  loss 
is  equal  to  the  moisture  in  the  sample  plus  three-quarters  of  its 
water  of  crystallization.  The  remaining  water  of  crystallization 
(one-quarter)  can  only  be  driven  off  at  a  heat  approaching  red- 
ness. 

To  obtain  from  these  data  the  actual  amount  of  moisture  present 
in  the  sample  apart  from  the  combined  water  or  water  of  crystal- 
lization, we  must  make  the  following  calculation. 

The  molecular  weight  of  anhydrous  sulphate  of  lime,  CaSO4, 
is  136.  Molecular  weight  of  the  crystallized  salt,  CaSO4,  2aq. 
=  172.  Molecular  weight  of  the  salt  dried  at  100°  C.,  €aSO4, 


4 

From  these  figures  we  may  form  the  proportion  as  145,  the 
molecular  weight  of  the  dried  salt,  is  to  172,  the  molecular  weight 
of  the  crystallized  salt,  so  is  (x),  the  weight  of  the  dried  sample 
to  (#),  the  equivalent  weight  of  c^stallized  salt  actually  present 
in  the  original  sample.  This  weight  (#)  deducted  from  the  original 


THJS  CHEMISTRY  OF  PAPER-MAKING. 


weight  of  the  sample  will  leave  the  actual  amount  of  moisture 
or  water  other  than  combined  water  which  was  expelled  from  the 
sample  at  100°  C. 

Sulphate  of  Magnesia  (JSpsom  Salts'). 

Symbol,  Mg$04,  7  aq.  —  Molecular  weight,  246. 

The  only  test  called  for  by  this  substance  is  for  the  presence  of 
metals,  iron,  and  lime. 

The  former  test  may  be  made  by  slightly  acidifying  a  solution 
of  the  salt  with  HC1  and  passing  sulphuretted  hydrogen  gas 
through  the  solution.  The  formation  of  a  colored  precipitate 
indicates  the  presence  of  some  of  the  heavy  metals.  The  solution 
may  be  tested  for  iron  sesquioxide  by  potassium  ferrocyanide  or 
sulphocyanide  (see  Testing  Alum  for  Iron  above). 

If  the  sample  is  well  crystallized  and  does  not  present  a  white, 
floury  appearance,  the  presence  of  sulphate  of  lime  in  much  more 
than  traces  can  hardly  be  expected. 

The  solution  may  be  tested  for  lime,  however,  by  adding  enough 
ammonium  chloride  solution  to  prevent  the  formation  of  a  pre- 
cipitate by  ammonia.  The  latter  is  then  added  in  excess  and  a 
little  ammonia  oxalate  solution.  The  almost  immediate  formation 
of  a  fine  white  precipitate  indicates  the  presence  of  lime. 

Sulphate  of  Zinc  (White  Vitriol). 
Symbol,  ZnSO*  ,  7  aq.  —  Molecular  weight,  287. 

Sulphate  of  iron  is  a  common  impurity  in  this  salt  and  may  be 
tested  for  as  under  Sulphate  of  Magnesia,  which  see,  and  the  amount 
of  iron  oxide,  F2O3,  may  be  determined  if  desired,  by  precipitation, 
with  excess  of  ammonia,  and  igniting  the  precipitate  after  careful 
washing  and  weighing  as  Fe2O3 

Sulphate  of  Copper  (Blue  Vitriol  —  -  Blue  Stone). 
Symbol,  CuSO4,  6  aq.  —  Molecular  wfcight,  249.4. 

The  "blue  stone  "  of  commerce  almost  always  contains  more  or 
less  sulphate  of  iron.  This  may  be  recognized  by  adding  to  a 
solution  of  the  salt  ammonia  sufficient  to  redissolve  the  precipitate 


SULPHATES.  385 


of  cupric  hydrate  first  formed  to  form  a  clear,  deep  blue  solution. 
The  solution  is  then  filtered,  when  any  sesquioxide  of  iron  present 
will  remain  on  the  filter,  and  may  after  washing  be  recognized  by 
the  appropriate  tests. 

The  iron  sulphate  may  nearly  all  be  removed  by  dissolving  the 
"  blue  stone  "  in  hot  water  and  recrystallizing. 

Sulphate  of  Iron  {Copperas —  G-reen  Vitriol). 
Symbol,  FeSO4 ,  7  aq.  —  Molecular  weight,  278. 

The  only  test  of  this  salt  likely  to  be  of  use  in  a  paper  mill  is  a 
determination  of  the  amount  of  bleaching-powder  solution  required 
to  oxidize  or  rust  a  given  amount.  For  this  purpose  a  solution  of 
the  sulphate  of  iron  is  prepared  containing  25  grammes  to  1000 
c.c.  100  c.c.  of  this  solution,  equal  to  5  grammes  of  the  sample, 
are  diluted  to  at  least  500  c.c.  in  a  large  beaker,  and  acidified 
strongly  with  sulphuric  acid.  The  bleach  solution  it  is  proposed 
to  use  for  "rusting"  the  "copperas"  is  then  dropped  in  from 
a  burette,  with  constant  stirring,  until  a  drop  of  the  iron  solution 
removed  on  a  rod  no  longer  gives  a  blue  color  when  mixed  on  a 
porcelain  plate  with  a  drop  of  weak,  freshly  prepared  solution  of 
ferrocyanide  of  potassium.  The  number  of  cubic  centimetres  of 
bleach  solution  used  is  the  measure  of  the  amount  of  this  solution 
required  to  oxidize  or  "  rust "  5  grammes  of  the  copperas.  Th,is 
process  does  not  give  strictly  accurate  results,  but  a  sufficiently 
close  approximation  for  practical  work. 

Salt  Cake. 

This  is  a  residue  left  from  the  treating  of  common  salt  with 
sulphuric  acid  in  the  manufacture  of  muriatic  acid,  and  consists 
for  the  most  part  of  bisulphate  of  soda  with  varying  amounts  of 
neutral  sulphate  and  chloride  of  sodium. 

It  is  often  of  value  to  know  the  amount  of  free  acid  in  the 
sample.  By  free  acid  in  this  connection  is  meant  not  only  that 
which  is  actually  free  and  uncombincd  with  any  base,  but  also 
that  which  is  in  excess  of  the  amount  required  to  form  neutral 
sodium  sulphate,  Na2SO4,  and  which  is,  we  may  say,  loosely  com- 
bined as  sodium  bisulphate,  NaHSO4.  This  may  be  determined 
by  titrating  a  solution  of  the  salt  directly  with  standard  soda 


386  THE  CHEMISTRY  OF  PAPER-MAKING, 

solution,  as  previously  described  (see  Determination  of  Strength  of 
Sulphuric  Acid).  For  technical  purposes  it  is  rarely  necessary  to 
determine  bases,  other  than  soda  present,  in  salt  cake,  as  their 
amount  is  usually  slight. 

The  total  amount  of  neutral  sulphate  of  soda,  equivalent  to  the 
total  base  present,  may  be  readily  determined  by  adding  a  slight 
excess  of  ammonia  to  a  solution  of  about  I  gramme  of  the 
substance,  heating  till  the  smell  of  ammonia  can  no  longer  be 
perceived,  and  filtering  from  any  precipitate  of  alumina  and  iron 
oxides,  which  may,  after  washing,  be  ignited,  and  their  weight  de- 
termined if  desired,  and  evaporating  the  nitrate  and  washings  to 
dryness  in  a  platinum  dish  over  the  water-tdth.  When  thoroughly 
dry,  the  residue  should  be  ignited,  cautiously  at  first,  and  finally  to 
redness.  After  cooling  it  should  be  moistened  with  dilute  ammonia 
and  again  dried  and  ignited,  cooled  in  a  desiccator,  and  weighed  as 
neutral  sulphate  of  soda, 


CHLORIDES  (MURIATES). 

Chloride  of  Sodivm  (Common  Salt). 

Symbol,  NaCl.  —  Molecular  weight,  58.5. 
For  specific  gravity  of  solutions  and  per  cent,  of  NaCl  contained,  see  Appendix. 

Common  salt  usually  contains,  as  impurities,  small  amounts  of 
sulphate  of  lime  and  chloride  (or  sulphate)  of  magnesia,  and 
frequently  traces  of  salts  of  iron  and  alumina. 

The  method  of  analysis  of  sodium  chloride  will  serve  in  the 
main  for  all  the  commonly  occurring  chlorides.  For  the  determi- 
nation of  the  small  amounts  of  impurities,  a  convenient  quantity 
to  weigh  out  is  20  grammes.  This  is  dissolved  in  about  200  c.c. 
of  water  and  acidified  with  a  few  drops  of  hydrochloric  acid, 
The  solution^  filtered  if  necessary  from  any  insoluble  matter,  is 
rendered  alkaline  by  the  addition  of  ammonia  in  slight  excess, 
and  heated  to  near  boiling  until  all  odor  of  ammonia  has  dis- 
appeared, the  volume  of  the  solution  being  maintained  by  the 
addition  of  hot  distilled  water  from  lime  to  time  as  required.  The 
solution  is  filtered  from  the  alumina  and  sesquioxide  of  iron  pre- 
cipitated, and  the  precipitate  well  washed,  dried,  ignited,  and 
weighed.  The  lime  is  separated  from  the  filtrate  from  the  last 
precipitate  by;  the  addition  of  ammonia  oxalate  solution.  This 


CKLOX1IW8.  387 


should  be  added  to  the  hot  liquid,  and  after  boiling,  the  whole 
allowed  to  stand  in  a  warm  place  until  the  precipitate  has  settled. 
It  is  then  filtered  and  the  precipitated  oxalate  of  lime  washed  with 
hot  water,  dried,  and  ignited  as  strongly  as  possible  for  a  quarter- 
to  a  half-hour  or  longer  if  the  precipitate  is  in  any  considerable 
amount.  H  is  well  to  guard  against  error  at  this  point  by  igniting 
and  weighing  a  second  time,  and  repeating  until  two  consecutive 
weights  are  obtained  which  are  identical,  The  strong  ignition 
changes  the  oxalafce  of  lime  into  lime  or  calcium  oxide,  CaO, 
which  is  the  substance  weighed. 

The  filtrate  from  the  oxalate  of  lime  precipitate  is  rendered 
strongly  alkaline  by  ammonia,  and  some  phosphate  of  soda  solu- 
tion added,  and  after  stirring,  allowed  to  stand  for  some  hours  to 
separate  magnesia  as  the  double  phosphate  of  ammonia  and  mag- 
nesia. This  precipitate,  filtered  out  and  washed  with  a  solution 
of  ammonia  (1£  volumes,  of  strong  ammonia  to  8£  volumes  of 
water),  is  dried  and  ignited  strongly,  and  weighed  as  magnesium 
pyrophosphate,  which  multiplied  by  0,8604  gives  the  equivalent 
magnesia,  MgO. 

This  completes  the  estimation  of  bases  necessary. 

Sulphuric  acid  is  determined  in  a  solution  of  20  grammes  acidified 
with  hydrochloric  acid,  and  filtered,  if  necessary,  by  precipitation 
with  barium  chloride  (compare  estimation  of  SO3  in  Soda-Ash). 

For  the  determination  ol  chlorine,  10  grammes  of  the  sample 
are  weighed  and  dissolved  to  1000  c.c. 

100  c.c.  of  this  solution,  containing  1  gramme  of  the  sample, 
are  diluted  to  500  c.c.  and  50  c.c.  of  the  latter  solution,  equivalent 
to  0.1000  gramme  of  the  sample,  are  taken  for  the  test.  This  is 
placed  in  a  beaker,  and  a  small  bit  of  neutral  potassium  chro- 
mate  about  the  size  of  a  pin-head  added  and  dissolved,  which 
should  color  the  solution  a  light  yellow.  A  -J^-normal  solution  of 
silver  nitrate  (prepared  as  below)  is  then  dropped  in  from  a 
burette  (one  with  glass  cock  should  be  employed),  with  constant 
shaking  or  stirring.  Each  drop  as  it  falls  into  the  salt  solution 
produces  a  brick-red  spot  of  silver  chromate,  which,  so  long  as 
any  chlorine  remains  in  the  solution,  disappears  at  once  on 
stirring,  being  changed  into  white  silver  chloride.  So  soon, 
however,  as  all  the  chlorine  present  has  been  converted  into  silver 
chloride,  the  red  silver  chromate  remains  permanent,  and  a  single 
drop  of  the  silver  nitrate  solution  is  sufficient  to  give  a  perceptible 


388  THE  CHEMISTRY  OF  PAPER-MAKING. 

reddish  tinge  to  the  solution,  and  this  is  the  end  reaction.  The 
cubic  centimetres  of  silver  solution  used  are  then  read  off,  and  this 
number  multiplied  by  0.00355  gives  the  equivalent  weight  of 
chlorine,  or  by  0.00585  the  equivalent  weight  of  salt,  NaCl,  in 
substance  taken  (0.1000  gramme)  for  the  titration. 

The  yig-normal  silver  nitrate  solution  may  be  prepared  with 
accuracy  by  weighing  16.966  grammes  of  pure  silver  nitrate  and 
dissolving  in  distilled  water  to  make  1000  c.c. 

The  silver  nitrate  should  be  very  cautiously  fused  over  a  low 
flame  in  a  porcelain  crucible,  employing  only  just  sufficient  heat  to 
effect  the  fusion,  since  a  high  heat  might  decompose  a  portion  of 
the  salt.  The  mass  after  cooling  should  be  coai-sely  powdered  in  a 
clean  porcelain  mortar,  and  the  above-named  weight  of  the  powder 
taken  to  make  the  solution.  Only  pure  distilled  water  must  be 
used,  since  other  water  almost  always  contains  either  chlorides  or 
organic  matter,  either  of  which  would  precipitate  a  portion  of 
the  silver,  and  consequently  the  solution  would  not  be  strictly 
^normal. 

The  value  of  the  solution  may  be  tested,  and  if  not  strictly 
Jg-normal,  a  factor  for  its  reduction  to  the  latter  may  be  found 
by  titrating  a  weighed  amount  of  pure  NaCl  with  it  in  the  same 
wa}r  as  described  above. 

Pure  salt  may  be  readily  prepared  by  evaporating  a  filtered  solu- 
tion of  ordinary  salt  over  the  water-bath  until  only  a  small  amount 
of  liquid  remains. 

This  is  drained  from  the  crystals  of  salt  while  hot,  the  crystals 
quickly  rinsed  with  a  little  distilled  water,  and  redissolved  in 
distilled  water,  and  the  process  repeated  at  least  three  times 
in  all.  The  crystals  are  then  dried  at  100°  C.  and  preserved  for 


To  test  the  standard  silver  solution,  a  portion  of  the  chemically 
pure  salt  should  be  powdered,  and  the  powder  heated  nearly  to 
redness  to  expel  any  moisture,  and  transferred  while  quite  warm 
to  a  light  bottle  or  tube  having  a  well-fitting  glass  stopper.  After 
tube  and  contents  are  entirely  cold  they  are  weighed,  about  100 
grammes  are  shaken  into  a  beaker,  and  tube  and  contents  weighed 
again.  The  difference  between  the  first  and  second  weights  gives 
the  amount  taken  for  the  titration.  Suppose  we  have  taken  0.095 
grammes  of  salt  and  find  that  it  takes  17.2  c.c.  of  the  silver 
solution  to  give  a  perceptible  red  color  to  the  solution  (colored 


CHLORIDES.  389 


with  chromate  of  potash).  Then  the  value  of  our  solution  will  be 
/01095==aoo55282\  0.0055232  grammes,  NaCl,  per  cubic  centi- 
metre ;  or  if  we  wish  a  factor  to  reduce  our  solution  to  ^-normal 
cubic  centimetres,  we  may  find  it  by  the  proportion, 

0.0058o :  0.0055232  =  1 :  x,  the  required  factor. 

For  the  estimation  of  chlorine  by  titration  with  standard  silver 
solution,  as  above,  it  is  necessary  always  that  the  solution  be 
neutral  in  reaction.  An  acid  solution  may  be  rendered  neutral  by 
digestion  for  some  time  with  powdered  Iceland  spar,  which  is  pure 
calcium  carbonate.  An  excess  of  the  powder  does  not  interfere  in 
any  way  with  the  titration  so  that  it  need  not  be  filtered  out.  In 
some  cases  it  is  preferable  to  precipitate  the  chlorine  with  an  excess 
of  silver  nitrate  and  to  weigh  the  silver  chloride  after  gently 
igniting.  For  this  purpose  the  solution  of  the  chloride  should  not 
be  too  dilute,  and  should  be  slightly  acidulated  with  nitric  acid. 
The  solution  should  be  heated  and  the  silver  solution  (quite 
strong)  added  in  excess  and  the  solution  vigorously  stirred.  It 
should  then  be  allowed  to  stand  in  the  dark  until  the  silver  chlo- 
ride has  settled  clear.  It  is  then  thrown  on  a  filter  and  washed 
as  rapidly  as  possible  with  hot  water  thoroughly.  It  is  then  dried, 
removed  as  thoroughly  as  possible  from  the  filter  to  a  small, 
weighed  porcelain  crucible,  the  filter  burned  separately,  and  the 
ash  added  to  the  silver  chloride  in  the  crucible.  The  whole  is 
next  moistened  with  a  drop  of  nitric  acid  and  warmed  gently.  A 
drop  of  HC1  is  then  added  and  the  crucible  cautiously  warmed 
with  a  low  flame  until  the  silver  chloride  begins  to  melt.  It  is 
then  cooled  and  weighed.  The  weight  of  chloride  of  silver, 
A^Cl,  found  multiplied  by  0.2489  =  chlorine,  Cl,  or  multiplied  by 
0.40863  =  chloride  of  sodium,  NaCl. 

Magnesium  Chloride. 
Symbol,  MgCl2.  —  Molecular  weight,  95. 

Crystallize'd  Magnesium  Chloride. 
Symbol,  MgCl2,aq. 

This  salt  is  of  interest  to  the  paper-maker  mainly  on  account  of 
its  being  the  material  employed  in  the  Hermite  electric  bleaching 
process.  It  usually  contains  a  little  calcium  chloride,  CaCla,  and 


390  THE  CHEMISTRY  OF  PAPER-MAKING. 

frequently  a  little  sodium  chloride.  These,  however,  do  not  unfit 
it  for  the  above  purpose.  The  only  tests  necessary  for  this  sub- 
stance  are  a  determination  of  total  chlorine,  insoluble  matter,  and 
moisture. 

The  first  may  be  determined  by  titration  with  standard  silver 
solution,  in  the  filtered  solution  as  described,  under  Sodium 
Chloride. 

The  insolnble  matter  is  determined  by  simply  filtering  out  from 
the  aqueous  solution  and  weighing  after  ignition. 

The  determination  of  moisture  in  this  substance  is  somewhat 
difficult,  since  the  salt  does  not  part  with  all  its  water  at  100°  C., 
and  on  ignition  it  loses  beside  the  water  a  portion  of  its  chlorine. 
A  method  which  is  perhaps  the  simplest  of  all.  and  sufficiently 
accurate  for  technical  purposes,  is  to  first  determine  the  total 
chlorine  in  a  portion  of  the  sample.  A  second  portion  is  to  be 
quite  strongly  ignited  in  a  porcelain  crucible  and  weighed  after 
cooling1.  The  loss  will  be  the  water  together  with  more  or  less  of 
the  chlorine.  The  ignited  sample  is  next  boiled  with  water  and 
filtered  and  the  chlorine  determined  in  the  filtrate.  The  difference 
between  the  chlorine  found  in  this  and  the  original  sample  will 
represent  the  amount  of  chlorine  which  was  expelled  by  ignition. 
This  deducted  from  the  total  loss  of  the  sample  by  ignition  leaves 
the  water  in  the  sample. 

Calcium  Chloride. 
Symbol,  CaCLj.  —Molecular  weight,  111. 

This  salt  is  rarely  or  never  seen  at  present  in  a  paper  mill, 
but  as  it  has  also  been  proposed  for  use  in  electric  bleaching,  we 
note  it  here.  It  has  a  very  great  affinity  for  water,  so  great  that  a 
lump  of  the  solid  substance  left  exposed  to  the  air  will  in  a  few 
hours  attract  so  much  moisture  from  the  air  as  to  liquefy  itself. 

Tests  for  free  acid,  total  chlorine,  insoluble  matter,  and  moisture 
are  required  by  this  substance. 

Free  acid  may  be  detected  by  means  of  litmus  solution,  and,  if 
present,  may  be  directly  titrated  with  standard  soda. 

Total  chlorine  is  determined  exactly  as  in  the  case  of  sodium 
chloride.  In  the  absence  of  free  acid,  the  moisture  may  be  deter- 
mined by  the  loss  on  careful  ignition  to  a  heat  a  little  below 
redness.  If  free  acid  is  present,,  the  same  procedure  must  be 


HYPOCHLOR1TES.  391 


followed  as  described  for  the  determination  of  moisture  in  mag- 
nesium chloride. 

Sesquichloride  of  Iron. 
Symbol,  Fe2Cl6  .—Molecular  weight,  325. 

Solution  of  Sesquichloride  of  iron,  or  ferric  chloride,  is  occa- 
sionally employed  to  give  a  reddish  tinge  to  paper.  The  salt 
always  has  an  acid  reaction,  but  in  well-prepared  samples  the 
amount  of  free  aeid  is  plight,  and  the  solution  is  so  sparingly 
employed  that  it  may  usually  Ise  disregarded. 

It  is  frequently  desirable  to  know  the  actual  amount  of  iron 
contained  in  a  solution  of  this  salt  or  in  the  commercial  article. 
This  may  be  readily  determined  by  reducing  a  solution  of  the 
salt  with  zinc  and  sulphuric  acid  and  titrating  the  reduced  solur 
tioti,  after  diluting  largely  with  distilled  water,  with  standard 
permanganate  solution.  (Compare  estimation  of  iron  oxide  in 
alum,) 

If  it  is  desired  to  calculate  the  actual  amount  of  ferric  chloride 
equivalent  to  the  sesquioxide  of  iron  found,  it  may  be  done  by 
the  proportion  — 


23      e,C», 

160  :  325  =  Fe203  found  :  Fe2Cl6  equivalent  to  same. 

The  metal  iron  equivalent  to  the  sesquioxide  found  may  be 
foundry  the  proportion  — 

Fe,Os      2Fe 

160  :..  112  =  Fe^Og  found  :  equivalent  Pe. 


HYPOCHLOBITES. 

Caloium  Hypochlorite  {Chloride  of  Lime). 
Symbol,  Ca  2  CIO.  —  Melecular  weight,  143. 

Calcium  hypochlorite  constitutes  the  valuable  ingredient  in 
"  bleaching-powder,"  and  in  a  good  article  is  present  to  the  extent 
of  from  65  to  75  per  cent.  The  balance  of  "chloride  of  lime" 
consists  of  varying  proportions  of  moisture,  calcium  hydrate, 
calcium  carbonate,  calcium  chlorate,  and  calcium  chloride.  The 
only  one  of  all  these  substances  having  any  value  as  a  bleaching 
agent  in  an  alkaline  solution  such  as  a  solution  of  bleaching- 


392  THE  CHEMISTRY  OF  PAPER-MAKING. 

powder  always  is,  is  the  calcium  hypochlorite.  The  custom  of  the 
trade  is,  however,  to  reckon  the  value  of  bleaching-powder  in 
terms  of  "  available  chlorine  "  instead  of  in  terms  of  actual  calcium 
hypochlorite.  This  "available  chlorine"  is  in  fact  that  portion 
of  the  total  chlorine  contained  in  the  sample  which  is  actually  in 
combination  as  an  integral  part  of  the  bleaching  compound,  which 
is,  as  we  have  said,  calcium  hypochlorite,  and  the  percentage  of 
"  available  chlorine  "  is  to  the  equivalent  amount  of  calcium  hypo- 
chlorite as  71  is  to  143. 

Various  methods  have  been  proposed  for  the  determination  of 
"available  chlorine"  in  bleaching-powder.  The  method  of  sim- 
plest application,  and  all  things  considered  the  most  satisfactory 
method  for  this  determination,  depends  on  the  fact  that  hypo- 
chlorous  acid,  either  free  or  in  combination,  has  the  power  of 
converting  arsenious  acid  (As2O3)  into  arsenic  acid  (As2O6), 
and  in  doing  so  it  is  itself  reduced  to  hydrochloric  acid  or  a 
chloride. 

The  carrying  out  of  the  process  requires  a  deci-normal  solution 
of  arsenite  of  soda,  and  some  starch  paste  having  a  small  amount 
of  potassium  iodide  dissolved  in  it. 

The  arsenite  of  soda  solution  is  prepared  by  weighing  roughly 
30  grammes  of  pure  crystallized  carbonate  of  soda  or  about  12 
grammes  of  the  dry  salt,  and  dissolving  it  with  heat  in  about 
100  c.c.  of  distilled  water. 

4.95  grammes  accurately  weighed  of  chemically  pure  arsenious 
acid  is  added  to  the  solution,  and  the  whole  heated  nearly  to  boil- 
ing, best  in  a  covered  beaker,  until  the  arsenic  is  entirely  dissolved. 
This  solution  after  cooling  is  to  be  diluted  to  exactly  1000  c.c. 
with  distilled  water,  and  forms  the  deci-normal  solution  of  sodium 
arsenite,  1  c.c.  of  which  will  be  changed  to  sodium  arseniate  by,  or 
is  equivalent  to,  0.00355  grammes  of  active  (bleaching  or  hypo- 
chlorous)  chlorine. 

The  starch  paste  is  made  by  adding  a  very  little  starch,  pre- 
viously rubbed  up  with  a  little  water,  to  a  considerable  amount  of 
boiling  water,  and  after  cooling,  adding  a  very  little  potassium 
iodide  and  stirring  well. 

The  bleaching-powder  to  be  tested  should  be  well  mixed  and 
the  lumps  broken  down. 

3.55  grammes  are  then  to  be  weighed  on  a  glass  accurately  and 
transferred  to  a  small  porcelain  mortar,  and  rubbed  to  a  cream 


HTPOCHLOBITES.  393 


quickly  with  a  little  water.  More  water  is  then  added,  and  well 
stirred  with  the  pestle,  allowed  to  stand  for  a  moment  for  any 
lumps  to  settle,  and  the  turbid  liquid  poured  off  into  a  litre  flask. 
The  residue  in  the  mortar  is  again  ground  with  water,  allowed  to 
settle  for  a  moment,  and  the  liquid  decanted  into  the  litre  flask 
with  the  former,  and  the  grinding  and  decanting  repeated  as  long 
as  any  grains  remain  in  the  bottom  of  the  mortal'  after  decanting. 
The  mortar  and  pestle  are  finally  well  rinsed  and  the  rinsings 
added  to  the  solution  in  the  flask,  which  is  finally  made  to  the 
1000  c.c.  mark  and  well  shaken. 

100  c.c.  of  the  turbid  solution  is  then  measured  out,  without 
filtering  or  allowing  to  settle,  and  transferred  to  a  beaker,  and  the 
arsenic  solution  described  above  run  in,  slowly  and  with  thorough 
stirring,  from  a  burette.  From  time  to  time  a  drop  of  the  solu- 
tion should  be  removed  from  the  beaker,  by  means  of  the  glass 
stirrer,  and  brought  in  contact  with  a  drop  of  the  starch  paste 
previously  placed  on  a  white  porcelain  surface.  So  long  as  a 
trace  of  hypochlorite  remains  in  the  solution,  it  will  produce  a 
more  or  less  deep  blue  color  with  the  iodized  starch  paste.  The 
arsenic  solution  should  be  added,  drop  by  drop,  when  the  blue 
color  given  by  a  drop  of  the  solution  being  titrated  and  a  drop  of 
the  starch  begins  to  fade,  and  the  disappearance  of  the  blue 
altogether  marks  the  end  of  the  reaction.  The  number  of  cubic 
centimetres  of  the  arsenic  used  reads  directly  the  percentage  of 
available  chlorine  in  the  sample  when  the  above  weights  and 
measures  are  adhered  to. 

In  Europe  it  is  customary  to  employ  an  acid  solution  of  arsenic, 
made  by  dissolving  the  arsenious  acid  in  hydrochloric  acid  and 
diluting,  instead  of  in  carbonate  of  soda,  as  above.  The  results 
obtained  by  the  use  of  this  solution  are,  however,  apt  to  be  too 
high,  since  the  chlorate  present  acts  in  an  acid  solution  to  oxidize 
the  arsenious  acid  in  the  same  way  as  the  hypochlorite,  while  the 
former  is  entirely  without  action  on  the  arsenic  so  long  as  the 
solution  remains  alkaline. 

The  use  of  alkaline  arsenic  also  corresponds  more  nearly  to  the 
conditions  of  practice  in  the  use  of  bleaching-powder  solutions, 
where  the  oxidizing  or  bleaching  action  takes  place  in  strongly 
alkaline  solutions. 


394  THE  CHEMISTRY  OF  P APEX-MAKING. 

Magnesium  Hypochlorite. 
Symbol,  Mg  2  CIO.  —Molecular  weight,  127. 

&7  Magnesium  hypochlbrite  is  only  known  in  solution  and  is 
chiefly  interesting  as  being  the  bleaching  agent  in  the  Hermite 
electric  "bleaching  process.  It  is  the  main  product  of  the  elec- 
trolysis of  a  solution  of  magnesium  chloride  under  the  conditions 
of  this  process.  The  strength  of  a  solution  of  magnesium  hypo- 
chlorite  is  measured  in  terms  of  available  chlorine  or  active 
chlorine,  as  in  the  case  of  ordinary  pleach  ing-powder  solution  and 
is  determined  in  precisely  the  same  way. 

Potassium  Hypochlorite. 
Symbol,  KC1O  —Molecular  weight,  90.6. 

Sodium  Hypochlorite. 
Symbol,  NaCiO.  —Molecular  weight,  74.5. 

Both  these  hypochlorites  are  known  only  in  solution,  and  are 
made  by  decomposing  a  solntion  of  hypochlorite  of  calcium  by 
equivalent  quantities  of  carbonate  of  potassium  or  sodium.  The 
former  is  known  in  pharmacy  as  Javelle  water,  or,  "Eau  de 
Javelle,"  and  is  chiefly  employed  for  medicinal  purposes. 

Solution  of  hypochlorite  of  sodium  is  the  kt  chlorinated  soda"  of 
the  shops,  and  is  also  known  as  Labarraque's  disinfectant  solution. 
All  the  hypochlorite  solutions  possess  bleaching  and,  disinfecting 
properties,  dependent  upon  the  hypochiorous,  or  active,  chlorine 
present.  The  strength  of  all  is  expressed  in  terms  ot  available 
chlorine  and  is  determined  by  titration  with  deci-normal  solution 
of  arsenite  of  soda,  as  described  under  Hypoohlorite  of  Calcium. 

In  testing  solutions  of  hypochlorites,  it  is  convenient  to  weigh 
out  the  number  of  grammes  of  the  solution  corresponding  to  the 
molecular  weight  of  chlorine  (35.5  grammes)  and  make  up  to 
1000  c.c. 

100  c.c.  of  this  solution  is  measured  and  made  again  to  1000  c.c., 
and  100  c.c.  of  this  second  solution  is  taken  up  for  the  titration. 
The  number  of  centimetres  of  deci-normal  arsenic  solution  con- 
sumed will  then  indicate  directly  the  per  cents,  of  active  chlorine 
in  the  original  solution  without  any  calculation. 


NITRATES.  395 


ANTICHLORS* 

Antichlors  are  of  two  kinds:  The  first,  or  antichlors  proper, 
oppose  the  action  of  hypochlorous  acid,  either  free  or  combined, 
by  abstracting  its  oxygen  and  thus  leaving  the  chlorine  in  the 
form  of  hydrochloric  acid  (or  a  chloride),  whose  chlorine  is 
inactive. 

This  class  is  found  in  the  lower  oxides  of  sulphur,  as  sodium 
hyposulphite  (or  thiosulphate},  Na^S^Oj,  and  sulphurous  acid 
(SO2)  and  its  compounds,  the  sulphites  and  bisulphites. 

These  all  serve  to  break  up  the  hypochloroas  compound  as 
indicated  above*  They  are  all  to  l>e  tested  for  their  antichlorine 
strength,  if  we  may  be  allowed  the  use  of  the  term,  by  means  of  a 
deci -normal  solution  of  iodine,  the  preparation  and  use  of  which 
will  be  explained  under  Analysis  of  Bisulphite  Solutions  below, 
which  see. 

The  strength  of  an  aotichlor  is  conveniently  expressed  in  terms 
of  the  chlorine  which  it  will  serve  to  "kill,"  reckoned  in  per 
cents,  on  the  antichlor  tested.  1  c.c.  of  deci-nonnal  iodine  solu- 
tion is  equivalent  to  0.00355  grammes  of  active  chlorine  in  this 
sense. 

The  second  class  of  antichlors  consists  of  substances  which  are 
capable  of  absorbing  oxygen  or  chlorine,  as  the  case  may  be, 
from  the  hypochlorous  compound,  aad  of  combining  directly  with 
it. 

To  this  class  belong  turpentine  and  essential  oils  in  general 
which  absorb  oxygen  directly.  Tne  caustic  alkalis  and  ammonia 
are  also  antichlors  to  a  degree,  and  act  by  combining  directly  with 
chlorine  to  produce  chlorides. 

NITRATES. 

Nitrate  of  Potash  (Saltpetre). 
Symbol,  KNO, .  —  Molecular  weight,  101.1. 

The  impurities  in  commercial  saltpetre  are  small  amounts  of 
chloride  of  sodium  and  sulphate  of  potash,  a  little  moisture,  and 
organic  matter. 

The  chloride  of  sodium  is  calculated  from  the  chlorine  found 
by  titrating  a  solution  of  10  grammes  of  the  salt  with  standard 


396  THE  CHEMISTRY  OF  PAPER-MAKING. 

silver  nitrate  solution.     (Compare  determination  of  chlorine  in 
Chloride  of  Sodium  —  common  salt.) 

C*         NaCl 

35.5  :  58.5  ==  chlorine  found  ;  equivalent  sodium  chloride. 

Sulphate  of  potash  is  calculated  from  the  sulphuric  acid  (SO3) 
found  by  precipitating  a  solution  of  10  grammes  of  the  nitrate, 
acidified  with  a  few  drops  of  hydrochloric  acid,  with  barium 
chloride.  (Compare  Determination  of  Sulphuric  Acid  in  Soda  Ash.) 
The  proportion  is  — 

B04     JC3804 

80  : 174.2  =  S03  found  :  equivalent  sulphate  of  potash. 

The  moisture  and  organic  matter  are  determined  from  the  loss 
on  cautiously  fusing  10  grammes  of  the  sample  in  a  porcelain 
crucible,  covered,  over  a  very  low  flame.  As  soon  as  the  mass  is 
completely  fused,  the  heat  should  be  removed,  and  the  whole 
allowed  to  cool ;  and  when  completely  cold,  it  is  to  be  weighed. 
It  is  convenient  to  first  weigh  the  crucible  and  cover,  and  then 
weigh  in  to  it  10  grammes  of  the  nitrate  for  the  fusion. 

The  actual  KNO3  is  determined  by  difference  between  the  per- 
centage of  the  total  impurities,  determined  as  above,  and  100  per 
cent. 

Crude  saltpetre  often  contains  a  small  amount  of  nitrate  of 
soda,  but  except  in  special  instances  its  presence  is  unimportant, 


mtrate  of  Soda  (Chili  Saltpetre). 
Symbol,  NaNO8 .  —  Molecular  weight,  85. 

What  has  been  said  above  in  regard  to  nitrate  of  potash  applies 
equally  to  nitrate  of  soda,  with  the  exception  that  in  the  latter 
salt  the  small  amount  of  sulphuric  acid  present  is  to  be  considered 
as  combined  with  soda  instead  of  with  potash.  The  formula, 
then,  for  concerting  the  SO8  found  into  equivalent  sulphate  of 
soda  will  be 

SOa    NatSO* 

60  :  142  =  found  :  equivalent  Na-jSO^. 


ACETATES.  397 


Nitrate  of  Iron.  • 
Symbol,  Fe  3  NO3 .—  Molecular  weight,  242. 

This  always  occurs  in  commerce  as  a  solution. 

It  is  frequently  employed  for  the  same  purpose  as  ferric  chlo- 
ride (which  see),  and  by  dyers  is  employed  in  conjunction  with 
different  forms  of  tannin  solutions  in  dyeing  blacks,  and  hence  is 
frequently  called  "  black  liquor." 

The  only  test  called  for  by  this  substance  is  a  determination  of 
the  total  iron  oxide  it  contains.  For  the  method  compare  Sesqui- 
chloride  of  Iron. 

ACETATES. 

Acetate  of  Lead  (" Sugar  of  Lead"). 
Symbol,  Pb  2C2H3O2,  3  aq.  —  Molecular  weight,  379, 

Acetate  of  lead  is  almost  the  only  acetate  ever  employed  in 
a  paper  mill.  This  is  used  in  conjunction  with  a  bichromate  in 
the  production  of  the  canary-yellow  chromate  of  lead.  The  test  of 
this  substance  is  for  the  total  amount  of  soluble  lead  it  contains, 
and  this  is  calculated  to  the  acetate.  The  method  for  determining 
the  soluble  lead  present  consists  in  adding  to  a  filtered  solution  of 
the  salt,  which  should  be  rather  dilute  and  acidified  with  a  few 
drops  of  acetic  acid,  a  solution  of  bichromate  of  potash-  in  excess. 
The  liquid  should  be  well  stirred  and  allowed  to  stand,  in  a  warm 
place  until  the  precipitate  has  settled,  leaving  the  liquid  clear. 
It  is  then  to  be  filtered  through  a  filter  which  has  been  previously 
balanced  by  means  of  another  filter  on  the  opposite  scale-pan. 
The  precipitate  is  well  washed  with  hot  water,  the  washing  being 
continued  until  the  washings  come  off  colorless.  The  niter,  con- 
taining the  precipitate  is  then  dried,  together  with  its  companion 
filter,  in  the  water-oven  until  it  ceases  to  lose  weight;  and1  weighed, 
the  empty  filter  l>eing  placed  on  the  opposite  scale-pan.  The 
weight  of  the  chromate  of  lead  weighed,  multiplied  by  0  68947, 
equals  oxide  of  lead,  PbO.  The  equivalent  acetate  of  lead  may  be 
found  by  the  proportion  — 

PbO       Pb  2  0,11,0,,  3  aq. 

222 :          378          =  oxide  of  lead  found  :  equivalent  acetate  of  lead. 


898  THE  CHEMISTRY  OF  PAPER-MAKING. 

'  CHROMATES. 
Bichromate  of  Potash. 
Symbol,  K^Cr20T .  —  Molecular  weight,  296.2. 

Bichromate  of  potash  occurs  in  so  great  a  state  of  purity  as  to 
hardly  ever  call  for  a  test.  If,  however,  this  is  desired,  the  total 
amount  of  chromic  acid,  CrO3,  may  be  determined  by  precipitating 
a  solution  containing  a  known  amount  of  the  sample  by  means  of 
a  solution  of  pure  acetate  of  lead,  acidified  with  acetic  acid,  and 
weighing  the  resultant  lead  chromate  (compare  Acetate  of  Lead). 
Chromate  of  lead,  multiplied  by  0.31053,  equals  chromic  acid,  CrOa. 

Bichromate  of  Soda. 
Symbol,  Na.Cr,O, .  —  Molecular  weight,  263. 

This  salt  is  frequently  employed  for  the  same  purpose  as 
bichromate  of  potash  on  account  of  its  less  cost.  It  possesses  the 
disadvantage,  however,  of  being  somewhat  deliquescent.  The 
proportion  of  actual  chromic  acid,  CrO3,  may  be  determined  as  in 
bichromate  of  potash  if  desired.  Theoretically,  263  parts  of  this 
salt  will  precipitate  the  same  amount  of  lead  acetate  as  295,2  parts 
of  the  potassium  bichromate. 

MINERAL  COLORS. 
Chrome  Yellow  (Canary  Yellow —  Canary  Paste). 

Pure  chrome  yellow,  or  neutral  chromate  of  lead,  is  found  when 
solution  of  bichromate  of  potash  or  soda  is  mixed  with  a  solution 
of  a  neutral  salt  of  lead,  such  as  the  acetate  or  the  nitrate  of  lead, 
as  a  bright  yellow  precipitate.  It  is  entirely  insoluble  in  pure 
water,  and  only  slightly  soluble  in  dilute  mineral  acids.  In 
practice  it  is  often  formed  in  and  on  the  fibre  by  first  impregnating 
the  fibre  with  a  solution  of  sugar  of  lead  in  tlie  beating  engine,  and 
then  adding  a  solution  of  bichromate. 

It  occurs  in  commerce  both  as  a  dry  powder  and  in  the  form  of 
paste.  The  former  is  little  liable  to  adulteration,  as  any  addition 
would  tend  to  change  the  shade  of  color. 

The  canary  paste  is,  however,  sometimes  falsified  by  a  judicious 
addition  of  ochre,  clay,  or  barytes,  with  the  aid  of  one  of  the 


MINERAL   COLORS.  399 


brilliant  yellow  "aniline,"  or  **azo"  colors,  or  even  picric  acid. 
Mineral  additions  may  be  detected  by  treating  a  sample  of  the 
paste  with  weak  caustic  potash  solution,  which  dissolves  lead 
chromate  to  a  clear  yellow  solution,  while  any  of  the  mineral 
adulterants  likely  to  be  present  would  remain  undissolved  by  the 
potash. 

The  presence  of  "azo"  colors  may  be  detected  by  treating  a 
sample  of  the  paste  with  strong  alcohol.  If  only  chromate  of 
lead  is  present,  the  alcohol  will  remain  colorless,  while  the  other 
yellows  will  "be  dissolved  and  will  appear  in  the  alcohol. 

Besides  the  canary  or  neutral  chromate  of  lead  there  are  basic 
lead  chromates,  varying  in  tint  all  the  way  to  a  brick-red  or  even 
crimson,  some  of  them  even  rivalling  vermilion  in  beauty  and 
brilliancy. 

Orange  Mineral. 

This  is  a  manufactured  lead  pigment  made  by  roasting  the 
carbonate  of  lead  under  special  conditions  as  regards  temperature 
and  access  of  air  to  the  furnace. 

On  boiling  with  a  considerable  quantity  of  moderately  dilute 
hydrochloric  acid,  orange  mineral  should  dissolve  without  residue 
to  a  colorless  solution.  The  solution  should  give  no  red  color 
with  potassium  sulphocyanide,  indicating  that  oxide  of  iron  is 
absent. 

Venetian  Red. 

Venetian  red  is  a  nearly  pure  aesquioxide  of  iron,  and  may  be 
obtained  in  quite  a  variety  of  shades,  the  different  shades  being 
imparted  to  it  by  roasting  at  various  temperatures  and  under 
various  other  conditions. 

The  pigment  should  be  nearly  all  soluble  in  strong  hydrochloric 
acid  on  "heating  with  it.  The  small  amount  insoluble  should  be  of 
a  pure  white  color  after  washing. 

The  hydrochloric  acid  solution  boiled  with  excess  of  ammonia 
and  filtered  from  the  ferric  hydrate  precipitated,  should  give, 
when  tested  with  ammonium  oxalate  solution,  only  a  small  pre- 
cipitate of  oxalate  of  lime. 

A  portion  of  the  hydrochloric  acid  solution  tested  with  barium 
chloride  solution  should  give  but  a  slight  precipitate. 


400  THE  CHEMISTRY  OF  PAPER-MAKING. 


Indian  Red. 

This  is  a  mineral  of  complex  composition  which  owes  its  color 
to  a  compound  of  ferric  oxide.  It  should  yield  to  boiling  hydro- 
chloric acid  a  moderate  quantity  of  sesquioxide  of  iron. 

Prussian  Blue  or  Berlin  Blue. 

This  is  a  ferrocyanide  of  iron.  A  pure  Prussian  blue  should  be 
odorless,  of  a  bright  blue  color,  with  a  coppery  lustre.  It  should 
yield  »o  thing  to  water  or  to  dilute  hydrochloric  acid.  On  igni- 
tion, it  should  smoulder  like  tinder.  The  ignited  residue  should 
be  entirely  soluble  in  strong  hydrochloric  acid  by  continued  heat- 
ing with  the  same.  The  solution,  after  the  precipitation  of  sesqui- 
oxide of  iron  by  the  addition  of  an  excess  of  ammonia,  should  give 
no  precipitate  on  the  addition  of  ammonium  oxalate  solution. 

Ultramarine. 

Ultramarine  is  a  peculiar  compound  of  complex  composition. 
The  color  is  very  sensitive  to  acids,  being  rapidly  discharged  by 
all  the  mineral  acids  even  when  very  dilute.  This  character 
serves  to  distinguish  it  from  Prussian  blue.  On  the  other  hand, 
alkalis  have  no  action  on  this  color,  while  the  color  of  Prussian 
blue  is  discharged  by  them. 

An  admixture  of  Prussian  blue  with  ultramarine  may  be  recog- 
nized by  treating  the  sample  with  a  moderately  strong  solution  of 
caustic  soda,  and  filtering.  The  filtered  solution  is  then  acidified 
with  hydrochloric  acid  and  a  few  drops  of  feme  chloride  solution 
added.  If  Prussian  blue  were  originally  present,  the  addition  of 
the  ferric  chloride  will  determine  the  formation  of  the  same  color 
in  this  solution. 

OtJie r  Mine ral  Colo rs 

of  use  to  the  paper-maker  are  certain  colored  clays  known  as 
ochres.  These  may  be  obtained  of  almost  any  shade  from  that 
of  sienna  and  Vandyke  brown  to  a  cream-white.  They  all  owe 
their  color  to  sesquioxide  of  iron  in  varying  proportions  and  com- 
binations. In  most  instances  the  iron  oxide  may  be  all  removed 
by  treatment  with  boiling  hydrochloric  acid,  leaving  a  pure  white 
lesidual  clay. 


ANILINE  COLORS.  401 


With  these,  as  with  clays  proper,  the  technical  test  is  more 
mechanical  than  chemical  and  relates  to  the  fineness  of  the 
material  and  its  freedom  from  grit.  The  presence  of  grit  may  be 
detected  roughly  by  rubbing  a  bit  of  the  sample  between  the  teeth 
when  the  presence  of  gritty  particles  may  be  felt. 

The  character  of  the  grit  and  its  approximate  amount  may  be 
determined  by  a  flotation  experiment  as  follows :  — 

A  considerable  quantity  of  the  material,  say  100  grammes,  is 
well  stirred  with  a  pailful  of  water,  best  in  a  glazed  earthenware 
jar.  It  is  then  allowed  to  stand  at  rest  for  a  few  moments,  five 
minutes  perhaps,  for  the  heavier  particles  to  deposit,  and  the  milky 
portion  carefully  poured  off  from  the  sediment.  This  is  again 
stirred  with  a  fresh  portion  of  water  and  poured  off,  and  the  pro- 
cess continued  until  the  water  becomes  almost  clear  in  the  time 
allotted. 

The  sediment  remaining  is  then  transferred  to  a  small  beaker 
and  allowed  to  deposit,  arid  finally  the  water  is  drained  off  as 
closely  as  possible  and  the  sediment  dried  and  weighed.  It  may 
then  be  examined  with  a  glass  or  otherwise  as  desired.  If  time 
enough  is  given  for  depositing  each  time,  this  sediment  will  con- 
tain all  the  grit  of  the  sample. 

In  the  matter  of  clays  it  is  often  of  advantage,  in  judging  of  the 
character  of  a  clay  as  to  its  suitableness  for  use  in  paper,  to  have 
a  complete  analysis  of  it,  since  what  might  pass  as  clay  under  an 
ordinary  inspection  an  analysis  might  prove  to  be  an  entirely 
different  substance  and  one  which  might  not  be  well  retained  in 
the  paper,  or  if  retained  might  give  an  undesirable  harshness  or 
other  quality  to  the  sheet. 

An  analysis  of  this  kind  would,  however,  necessarily  be  made 
by  a  professional  chemist. 

All  the  mineral  colors  and  clays  are  insoluble  in  water,  and  in 
the  paper  remain  on  the  surface  of  and  between  the  fibres  of  the 
sheet. 

ANILINE  COLORS. 

The  **  aniline  colors,"  on  the  other  hand,  as  well  as  carmine,  are 
all  soluble  colors  and  penetrate  the  fibre.  The  only  test  to  be 
applied  to  these  colors  is  one  which  has  in  view  to  determine 
comparatively  the  intensity  of  the  tinctorial  power,  or,  in  other 


402  THE  CHEMISTRY  OF  PAPER-MAKING. 

words,  the  comparative  strength  of  different  samples  relatively  to 
their  cost. 

This  is  known  as  the  "  money-value  test." 

In  applying  this  test,  we  do  not  weigh  equal  amounts  of  each 
.sample  if  their  price  per  pound  is  different,  but  that  amount  of 
each  which  the  same  amount  of  money  will  buy  for  the  several 
amounts  to  be-  taken  for  the  test.  For  example,  if  we  wish  to 
compare  three  different  samples  of  soluble  blue  costing,  say 
16  cents,  20  cents,  and  28£  cents  respectively,  we  would  weigh  1.6 

grammes  of  the  first,  ££  of  1.6  grammes  =  1.28  grammes  of  the 

Tfl 
secondhand—-  of  1.6  grammes  =  1.0893  grammes  of  the  third, 

23£ 
and  dilute  the  solution  of  each  of  these  amounts  to  1000  c.c. 

A  convenient  amount  (say  10  or  20  c.c.)  of  the  solution  made 
from  the  lowest  priced  sample  is  next  placed  in  a  tall  narrow 
bottle,  or  jar  of  clear  glass,  and  diluted  to  a  rather  light  tint  with 
water,  noting  the  amount  of  water  added.  The  same  amount  of 
each  of  the  other  solutions  is  then  measured  and  diluted  in  similar 
bottles  or  jars,  until  the  depth  of  the  tint  of  the  solutions  matches 
that  of  the  first  solution  diluted,  and  the  volume  of  the  water 
required  noted  in  each  case.  Then  suppose  we  have  diluted  our 
first  sample  to  100  c.c.,  10  c.c.  of  the  strong  solution  being  taken  ; 
the  second  requires  86  c.c.  of  water  to  match  the  shade,  making 
96  c.c.  in  this  ;  and  the  third  requires  120  c.c.  -  -  making  130  c.c. 
in  all. 

Then  the  tinctorial  values  of  the  three  samples  will  be  as  100. 
96,  and  1  30  per  unit  of  cost,  while  their  cost  per  unit  of  weight 
was  as  16,  20,  and  23£,  respectively.  Graphically  expressed,  the 
result  of  the  test  we  have  cited  would  be  :  — 

1  Ib.  @  16  cts.  will  color  to  a  given  shade  100  Ibs.  of  pulp, 
0.8  Ib.  @  20  cts.  will  color  to  a  given  shade  96  Ibs.  of  pulp, 
0.68  Ib.  @  23J  cts.  will  color  to  a  given  shade  130  Ibs.  of  pulp; 

and  conversely,  to  color  100  Ibs.  of  pulp  to  a  given  shade  will 
require  of 

Sample  1,  @  16    cts.,  1         Ib.,  costing  16    cts.  ; 

Sample  2,  @  20    cts..  0.833  Ib.,  costing  16|  cts.  ; 

Sample  3,  @  23£  cts.,  0.523  Ib.,  costing  12£  cts.  ;    < 


showing  that  in  the  case  we  have  taken  for  example  the  best  is 
the  cheapest  to  use,  while  that  costing  the  lowest  price  per  pound 


WATER  ANALYSIS,  403 


stands  second  in  the  list,  and  the  sample  at  the  medium  price 
proves  to  be  the  most  expensive  of  the  three. 

This  method  of  "  money-value  testing "  is  largely  adopted  by 
dealers  in  dyes  and  extracts;  and  while  not  giving  absolute  values 
in  per  cents,  of  actual  color  present,  it  furnishes  comparisons 
which  could  hardly  be  arrived  at  in  any  other  way  and  which  are 
often  of  much  value. 

WATER   ANALYSIS. 

No  single  element  in  the  location  of  a  paper  mill  is  deserving  of 
more  consideration  than  that  of  the  water  supply.  Not  only  for 
use  in  steam-generating  boilers,  but  for  the  other  purposes  of  the 
paper-maker,  an  abundant  supply  of  water  of  good  quality  is  of 
the  highest  importance. 

The  only  means  of  judging  beforehand  of  the  character  of  a 
water  lies  in  a  more  or  less  complete  chemical  examination.  The 
color,  smell,  and  taste  of  a  water  are,  as  far  as  they  go,  indications 
of  its  probable  character,  but  it  must  be  borne  in  mind  that  a 
water  having  the  characteristics  of  good  color,  taste,  and  smell 
may  be  heavily  charged  with  very  troublesome  mineral  matters, 
while,  on  the  other  hand,  one  in  which  these  characteristics  are 
had,  may  still  contain  little  which  will  interfere  with  the  opera- 
tions in  which  it  is  to  be  employed. 

Hardness. 

Considerable  information  in  regard  to  the  suitableness  of  a 
water  for  boiler  use  may  be  obtained  by  testing  the  "  hardness,"  or, 
in  other  words,  the  soap-destroying  power  of  a  water. 

Those  mineral  substances  occurring  in  water  which  have  a 
tendency  to  corrode  a  boiler,  or  to  produce  scale,  have  also  the 
property,  in  general,  of  decomposing  a  solution  of  soap  with  the 
formation  of  an  insoluble  metallic  soap,  so  that  the  measure  of 
the  soap-destroying  power  will  be  roughly  a  measure  of  the 
"scale-formers"  in  the  water. 

Free  acids  also  have  the  power  of  decomposing  soap  solutions 
by  combining  with  the  alkali  of  the  soap  and  setting  free  the 
fatty  acids.  All  the  josults  obtained  in  water  analysis  are  from 
custom  generally  expressed  in  grains  per  gallon. 

For  the  determination  of   the  hardness  of   water,   a   standard 


404  THE  CHEMISTRY  OF  PAPEE-MAKING. 

solution  of  soap  is  made  by  dissolving  10  grammes  of  good,  white 
Castile  soap  in  dilute  alcohol  (about  40  per  cent.)  to  make  1000  c.c. 
One  cubic  centimetre  of  this  solution  should  be  able  to  precipitate 
a  soluble  calcium  salt  equivalent  to  0.001  gramme  of  carbonate  of 
lime.  On  account  of  the  varying  amounts  of  moisture  in  Castile 
soap,  however,  it  is  only  as  we  may  say  by  accident  that  we  are 
able  to  obtain  from  10  grammes  of  soap  a  solution  of  exactly  this 
strength.  It  is  always  necessary  then  to  verify  the  soap  solution 
by  an  actual  experiment  upon  water  containing  a  known  amount 
of  a  calcium  salt.  For  this  purpose,  we  may  weigh  exactly  1 
gramme  of  powdered  marble,  or  Iceland  spar,  and  dissolve  it  in 
a  covered  beaker,  in  a  slight  excess  of  dilute  hydrochloric  acid. 
The  excess  of  acid  is  then  neutralized  by  ammonia  in  very  dight 
excess  and  the  solution  made  to  JOOO  c.c.  Each  cubic  centimetre 
of  this  solution  will  then  contain  lime  equivalent  to  0.001  gramme. 
In  order  to  test  the  standard  soap  solution,  10  c.c.  of  the  dilute 
lime  solution  just  mentioned  is  measured  accurately  and  placed  in 
a  wide  bottle  or  flask  holding  about  200  c.c.  90  c.c.  of  distilled 
water  are  then  added  and  the  flask  shaken.  The  standard  soap 
solution  is  then  run  in  from  a  burette,  a  little  at  a  time,  the 
stopper  being  inserted  and  the  flask  vigorously  shaken  after  each 
addition  until  a  distinct  lather  is  formed  which  covers  the  sur- 
face of  the  liquid  in  the  flask,  and  which  will  remain  as  a  thin, 
unbroken  pellicle  for  five  minutes. 

The  lather  should  not  be  thick  and  frothy,  but  thin,  and  when  it 
breaks,  the  liquid  will  show  in  patches  beneath.  When  this  point 
is  reached,  the  number  of  cubic  centimetres  of  soap  solution  used 
is  read  off,  and  the  milligrammes-  of  carbonate  of  lime  equivalent 
to  each  cubic  centimetre  found  by  dividing  10,  the  milligrammes 
in  the  10  c.c.  of  lime  solution  used,  by  the  number  of  cubic  centi- 
metres of  soap  solution  employed. 

The  standard  soap  solution  will  preserve  its  strength  indefinitely 
if  kept  in  a  tightly  stoppered  bottle. 

The  total  hardness  of  a  sample  of  water  is  tested  by  measuring 
100  c.c.  of  the  sample,  and  treating  it  with  soap  solution  as 
described  above. 

If  100  c.c.  of  the  sample  are  found  to  consume  more  than  16  c.c. 
of  the  soap  solution,  a  less  quantity  of  the  water  must  be  taken 
and  diluted  to  100  c.c.  with  distilled  water  for  the  test,  as  the 
presence  of  any  considerable  amounts  of  lime  or  magnesia  soaps 


WATER  ANALYSIS.  405 


interferes  with  lathering,  and  consequently  with  the  accuracy  of 
the  test.  The  number  of  cubic  centimetres  of  soap  solution  con- 
sum  edt  multiplied  by  the  value  per  cubic  centimetre,  as  above 
determined,  gives  the  equivalent  carbonate  of  lime  in  milligrammes 
in  the  amount  of  water  taken  for  the  test.  This  figure  may  be 
converted  into  equivalent  grains  per  gallon  by  the  proportion  — 

Cubic-centimetres  employed  for  test :  cubic  centimetres  in  1  gallon  (3785) 
=  grammes  found  x  15.4 :  grains  per  gallon. 

It  will  be  noted  that  we  have  used  the  term  " equivalent"  car- 
bonate of  lime  above^  and  it  must  be  borne  in  mind  that  this  figure 
expresses  not  only  the  actual  carbonate  of  lirne  present,  but  includes 
also  the  iron  and  alumina,  and  sulphate  and  chloride  of  calcium 
and  magnesium  present,  expressed  in  terms  of  equivalent  carbonate 
of  lime. 

Carbonate  of  lime,  CaCO3,  is  almost  completely  insoluble  in  pure 
water,  but  in  those  waters  which  hold  carbonic  acid  in  solution,  as 
is  the  case  with  a  majority  of  natural  waters,  especially  those  of 
springs  and  deep  wells,  it  is  soluble  to  no  inconsiderable  extent.. 
The  carbonate  of  lime  thus  held  in  solution  by  carbonic  acid  gives 
to  a  water  what  is  called 


Temporary   Hardness. 

The  determination  of  the  temporar}?  hardness  of  a  water  is  of 
even  more  importance  in  determining  its  fitness  for  boiler  use  than 
is  the  determination  of  the  total  hardness,  especially  if  the  water 
contains  sulphate  of  lime,  since  on  boiling  the  carbonic  acid  is 
driven  off  and  the  carbonate  of  lime  previously  held  in  solution 
by  it  falls  in  the  shape  of  a  fine  powder.  Now,  if  sulphate  of 
lime  is  also  present,  it  is  gradually  deposited  as  the  water  evapo- 
rates, being  soluble  only  one  part  in  one  hundred  parts  at  60°  F. 
and  less  soluble  at  higher  temperatures,  and  serves  to  cement  the 
particles  of  carbonate  firmly  together  into  a  hard  crust  or  scale. 

The  temporary  hardness  of  a  sample  of  water  is  determined  by 
boiling  100  c.c,  of  the  water  in  a  flask  for,  at  least,  a  half-hour. 
It  is  then  cooled  and  again  made  to  100  c.c.  with  distilled  water 
and  titrated  with  the  standard  soap  as  described  above.  The 
number  of  cubic  centimetres  of  standard  soap  used  calculated  to 
equivalent  carbonate  of  lime,  and  this  again  to  equivalent  grains 


406  THE  CHEMISTRY  OF  PAPER-MAKING. 

per  gallon,  gives  the  permanent  hardness  of  the  sample.  The 
difference  between  the  permanent  and  the  total  hardness  is  the 
temporary  hardness. 

Clark's  process  for  softening  water  consists  in  the  removal  of 
the  temporary  hardness  by  the  addition  of  a  small  quantity  of 
caustic  lime,  which  combines  with  the  carbonic  acid  present  to 
remove  it  from  solution  as  carbonate  of  lime.  The  removal 
of  the  carbonic  acid  also  allows  the  carbonate  of  lime  which  it  had 
previously  held  in  solution  to  be  precipitated,  and  thus  destroys 
the  temporary  hardness. 

Clark's  process  is  of  no  value  as  regards  permanent  hardness. 

A  water  which  shows  by  the  soap  test  a  permanent  hardness  of 
only  two  or  three  grains  of  CaCO8  per  gallon  with  no  temporary 
hardness,  and  whose  reaction  is  neutral  or  faintly  alkaline  to  litmus, 
may  with  very  little  question  be  considered  fit  for  use  in  a  steam 
boiler. 

On  the  other  hand,  the  hardness  of  a  water  as  measured  by  the 
soap  test  does  not  necessarily  condemn  its  use  in  a  boiler.  It  indi- 
cates, however,  the  desirability  of  a  more  extended  chemical  exam- 
ination before  deciding  on  its  fitness  for  that  purpose.  Sulphate 
of  magnesium,  for  instance,  would  decompose  soap,  and,  if  this 
substance  alone  were  present,  a  water  might  show  almost  any 
degree  of  hardness,  but  such  a  water  would  never,  under  ordinary 
circumstances,  form  scale  in  a  boiler. 

If  the  soap  test  has  indicated  that  a  further  examination  of  the 
water  is  advisable,  we  next  proceed  to  determine  the 

Total  Solids. 

For  this  purpose,  having  cleaned,  ignited,  and  weighed  a  plati- 
num dish,  we  place  in  it  100  c.c.  of  the  water  and  evaporate  it  to 
dryness  over  the  water-bath.  If  only  a  very  little  residue  appears 
to  be  left,  it  is  well  to  evaporate  150  c.c.  more,  making  -J  litre  in 
all,  to  dryness  in  the  same  dish.  The  residue  is  then  heated  to 
130°  C.  in  an  air-bath,  and.  after  cooling  is  weighed.  This  gives, 
deducting  the  weight  of  the  dish,  the  total  solid  matter  in  the 
amount  of  water  evaporated,  and  this  is  to  be  calculated  into 
grains  per  gallon  by  the  proportion  — 

cubic  centimetres  evaporated  :  cubic  centimetres  in  1  gallon  =  grammes 
weighed  x  15.4  :  grains  per  gallon. 


WATER  ANALYSIS.  407 


The  dish  is  then  ignited  at  a  low  red  heat  until  the  residue  is 
white.  After  cooling,  the  residue  is  moistened  with  a  solution  of 
ammonium  carbonate,  or,  better  still,  with  a  little  carbonic  acid 
water  (a  syphon  of  "  soda  water "  answers  the  purpose  well),  to 
replace  any  carbonic  acid  which  may  have  been  driven  off  by  the 
ignition,  and  again  dried  over  the  water-bath,  heated  to  180°  C., 
cooled,  and  weighed.  The  weight  of  the  last  residue  gives  the 
total  mineral  matter  present,  and  this  deducted  from  the  first 
residue,  or  the  total  solids,  gives  the  organic  and  volatile  matter 
by  difference* 

The  amount  of  the  inorganic  or  mineral  solids  obtained  from 
the  portion  evaporated  as  above  will  serve  to  determine  how  much 
of  the  sample  must  be  concentrated  for  the  examination  of  the 
mineral  constituents*  Enough  should  be  taken  to  give  at  least 
1  gramme  of  total  mineral  matter.  Two  grammes  would  be  pref- 
erable, if  the  evaporation  of  the  requisite  amount  of  the  sample 
is  not  too  tedious.  The  sample  to  be  aevaporated  for  the  latter 
purpose  should  be  acidified  with  a  few  drops  of  hydrochloric  acid, 
and  evaporated  in  a  platinum  dish  over  the  water-bath,  adding  a 
portion  of  the  sample  from  time  to  time  as  it  evaporates,  until  it 
has  all  been  transferred  to  the  -dish.  It  is  finally  evaporated  to 
dryness,  and,  after  breaking  down  any  lumps  with  a  glass  rod,  is 
heated  over  the  water-bath  until  the  residue  no  longer  smells  of 
hydrochloric  acid,  in  order  to  render  insoluble  any  silica  that  may 
be  present.  After  cooling,  it  is  moistened  with  hydrochloric  acid, 
and  taken  up  with  water,  and  the  solution  filtered  from  insoluble 
matter,  which  latter  will  consist  of  the  silica  and  very  likely  a 
little  organic  matter.  This  is  well  washed  over  the  filter  with  hot 
water  and,  after  drying,  ignited  and  weighed.  The  organic  matter 
will,  of  course,  be  destroyed  by  the  ignition  leaving  the  silica 
pure  white. 

To  the  combined  filtrate  and  washings  from  the  silica  ammonia 
is  added  in  slight  excess,  and  the  whole  heated  very  nearly  to 
boiling  for  some  time,  until  the  odor  of  ammenia  can  no  longer  be 
detected.  This  serves  to  separate  any  alumina*  and  sesquioxide 
of  iron,  and  these  should  be  filtered  out  and  well  washed  with 
hot  water,  dried,  ignited,  and  weighed.  The  filtrate  and  wash- 
ings should  next  be  concentrated  to  100  c.c.  or  less,  and 
an  excess  of  ammonium  oxalate  solution  added  to  separate  the 
lime,  Both  the  solutions  should  be  hot  before  being  mixed; 


408  THE  CHEMISTRY  OF  PAPER-MAKING. 

otherwise  the  oxalate  of  lime  is  apt  to  precipitate  in  a  very 
finely  divided  condition  and  to  give  trouble  by  passing  through 
the  filter.  The  solution,  after  the  oxalate  is  added,  should  be 
kept  hot  for  a  little  time,  until  the  precipitate  has  settled  nearly 
clear.  It  is  then  filtered,  and  the  precipitate  washed  with  hot 
water.  The  oxalate  of  lime  precipitate  is  dried,  and  ignited 
strongly  for  some  time,  and  weighed.  After  weighing,  it  should 
again  be  ignited  and  weighed,  and  this  repeated  until  a  constant 
weight  is  obtained.  The  final  weight  is  the  weight  of  the  lime, 
CaO,  present.  The  filtrate  and  washings  from  the  oxalate  of  lime 
are  allowed  to  become  cold,  and  then  a  large  excess  of  ammonia  is 
added  and  some  solution  of  pure  phosphate  of  ammonia  to  pre- 
cipitate the  magnesia.  After  stirring,  this  is  allowed  to  stand  for 
several  hours  for  the  precipitation  of  the  magnesia  to  become 
complete.  The  precipitate  is  then  filtered  off,  and  washed  with  a 
mixture  of  8J  parts  by  volume  of  water  and  1£  parts  of  strong 
ammonia.  The  precipitate  is  dried  and  ignited  strongly,  and 
weighed  as  magnesium  pyrophosphate,  Mg2P2O7,  which  multi- 
plied by  0.3604  gives  the  equivalent  magnesia,  MgO. 

This  completes  the  separation  of  all  the  bases  ordinarily  present 
in  water  except  the  alkalis.  For  the  determination  of  these,  the 
filtrate  from  the  magnesium  phosphate  precipitate  is  to  be  evapo- 
rated in  the  platinum  dish  to  dryness  and  ignited  gently  until  no 
more  fumes  appear,  taking  care  only  to  barely  fuse  the  residue. 
The  residue  is  dissolved  in  water  and  filtered  from  any  undissolved 
matter,  and  the  filter  well  washed.  The  filtrate  and  washings  are 
returned  to  the  clean  platinum  dish,  a  few  drops  of  ammonium 
chloride  solution  added,  and  again  evaporated  to  dryness  and 
ignited.  It  is  cooled  in  the  desiccator  and  weighed,  and  the  weight 
of  the  dish  deducted,  leaving  the  weight  of  the  mixed  chlorides  of 
sodium  and  potassium,  NaCl-fKCl.  The  chlorides  are  next 
dissolved  in  the  dish  with  a  little  water  and  some  solution  of 
platinic  chloride  added,  and  the  whole  evaporated  almost  to  dryness 
over  the  water-bath.  It  is  then  removed  from  the  bath  and  some 
80  per  cent,  alcohol  poured  over  the  mass  in  the  dish  before  it  has 
had  time  to  cool.  It  is  covered  and  allowed  to  rest  for  some  time 
and  then  filtered  through  a  small  filter,  which  has  been  tared  by 
means  of  a  similar  filter  placed  on  the  opposite  scale-pan,  and 
trimmed  until  the  two  exactly  balance. 

The   precipitate,   which    should  consist  of    platinochloride   of 


WATER  ANALYSIS.  40'J 


potassium,  K2Pt.Cl6,  should  be  bright  and  crystalline.  It  should 
be  washed  on  the  filter  with  80  per  cent,  alcohol  until  the  washings 
come  off  entirely  colorless.  The  precipitate  and  the  tared  filter 
should  be  dried  in  the  water-oven  and  weighed,  the  tared  filter  being 
placed  on  the  scale-pan  opposite  the  one  containing  the  filter 
carrying  the  precipitate.  The  weight  of  the  precipitate  multiplied 
by  0.1932  equals  equivalent  potash,  K2O,  or  multiplied  by  0.3057 
equals  equivalent  potassium  chloride,  KC1. 

The  weight  of  potassium  chloride  thus  found,  deducted  from 
the  weight  of  the  mixed  chlorides,  as  determined  above,  leaves  the 
weight  of  the  sodium  chloride,  NaCl,  and  this  multiplied  by  0.5306 
gives  the  equivalent  soda,  Na2O.  This  completes  the  determina- 
tion of  the  bases. 

A  separate  portion  of  250  or  500  c.c.  of  the  water  should  be 
measured  and  acidified  with  hydrochloric  acid  and  evaporated  to  a 
small  volume,  say  about  100  c.c.  for  the  determination  of  sulphuric 
acid,  SO8 .  The  concentrated  water  should  be  filtered  if  necessary 
and  an  excess  of  barium  chloride  solution  added,  and  the  SO3 
weighed  as  barium  sulphate  (compare  determination  of  SO3  in 
Soda  Ash). 

Still  another  portion  of  250  or  500  c.c.  is  to  be  taken  for  the 
determination  of  chlorine,  CL  This  portion  should  be  evaporated 
without  the  addition  of  acid  to  about  50  c.c.,  and  after  cooling, 
titrated  with  standard  silver  nitrate  solution  by  the  aid  of  chromate 
of  potash  (compare  estimation  of  chlorine  in  Sodium  Chloride). 

This  completes  the  examination  of  the  solid  residue,  it  being 
rarely  necessary  to  make  a  determination  of  carbonic  acid  directly. 
As  yet,  however,  we  have  very  little  knowledge  of  the  character 
of  the  mineral  matter  present  in  the  water  we  have  examined,  and 
to  obtain  such  knowledge,  it  is  necessary  to  translate  the  language 
of  our  analytical  data  into  that  of  the  several  compounds,  as  they 
exist  in  the  original  sample.  Experience,  coupled  with  direct 
experiment,  has  shown  the  manner  of 

Grouping  the  Constituents 

to  be  as  follows :  The  chlorine  is  combined  with  soda  as  sodium 
chloride,  NaCl.  Any  excess  of  chlorine  over  that  required  by  the 
soda  found  is  combined  with  potash,  magnesia,  and  lime  in  turn. 
Any  excess  of  soda  over  that  required  to  form  NaCl  with  the 


410  THE  CHEMISTRY  OF  PAPER-MAKING. 

chlorine  is  calculated  to  sulphate  oi  soda,  Na2SO4,  and  the  re- 
mainder of  the  sulphuric  acid  is  to  be  combined  with  potash, 
magnesia,  and  lime  in  the  order  named.  Any  excess  of  bases  yet 
remaining  uncombined  is  to  be  calculated  to  neutral  carbonates. 

The  sum  of  all  these  compounds,  together  with  the  iron  oxide, 
alumina,  and  silica  formed,  expressed  in  grains  per  gallon  should 
he  equal  to  the  grains  per  gallon  calculated  from  the  determina- 
tion of  the  total  inorganic  solids  to  the  fraction  of  a  grain,  other- 
wise the  work  must  be  repeated. 

As  hefore  remarked,  carbonate  of  lime  is  very  nearly  insoluble 
in  water  and  yet  in  the  water  residue  and  in  boiler  scale  we 
often  find  it  present  in  considerable  amount;  the  explauation  of 
this  seeming  paradox  being  that  the  original  water  wa&  a  dilute 
solution  of  carbonic  acid,  and  that  in  this  solution,  carbonate  of 
lime  is  quite  appreciably  soluble.  When,  however,  the  water  is 
heated,  the  free  carbonic  acid  is  driven  out  of  the  solution,  and 
the  water  being  no  longer  able  to  hold  the  carbonate  in  solution, 
it  falls  as  a  precipitate,  and  is  found  in  the  residue  or  in  the 
scale,  which  is  really  the  same  thing.  A  water  which  contains 
even  two  or  three  grains  of  sulphate  of  lime  per  gallon  is  unfit 
for  use  in  a  boiler  unless  precautions  are  taken  to  guard  against 
the  formation  of  scale,  and  especially  if  it  also  shows  temporary 
hardness  under  the  soap  test.  Carbonate  of  lime  alone  (which 
is  indicated  by  temporary  hardness)  makes  mud  rather  than 
scale ;  but  if  sulphate  of  lime  is  also  present,  the  latter  seems  to 
act  as  a  cementing  material  to  make  the  carbonate  into  stone  on 
the  boiler  sheets,  etc.  The  addition  of  soda-ash  in  the  proper 
proportion  to  water  showing  temporary  hardness  and  sulphate  of 
lime  will  overcome  the  scaling  tendency  almost  entirely,  but  will 
cause  a  large  amount  of  mudy  to  get  rid  of  which,  the  boilers  must 
be  blown  out  frequently. 

Waters  containing  silica  are  especially  troublesome,  giving  a 
hard,  closely  adherent  scale,  sometimes  approaching  feldspar  in 
composition.  Soda-ash  may  also  be  employed  with  advantage  with 
waters  of  this  class.  In  every  case,  however,  soda-ash  should  be 
looked  upon  rather  as  a  preventive  than  a  cure,  since  it  will  only 
seldom  serve  to  loosen  up  a  scale  already  formed. 

Many  so-called  scale  preventers  are  in  the  market,  and,  like 
other  patent  medicines,  some  of  them  are  probably  of  value. 
Petroleum  oil,  either  crude  or  refined,  is  among  the  best  of  scale 


WATER  ANALYSIS.  411 


preventers,  and  is  equally  useful  with  almost  every  character  of 
water  which  is  likely  to  form  scale.  Its  probable  action  is  one  of 
lubrication,  preventing  by  its  presence  the  cementation  of  the 
solid  particles,  and  keeping  the  deposit  in  the  form  of  mud,  in 
which  state  it  is  easily  gotten  rid  of.  Organic  impurities,  unless 
present  in  very  excessive  amount,  are  of  no  very  serious  impor- 
tance as  regards  the  use  of  water  in  steam  boilers,  as  they  seldom 
form  heavy  deposits. 

For  Manufacturing  Purposes. 

For  other  purposes,  a  knowledge  of  the  amount  and  character 
of  the  impurities  in  water  is  of  even  greater  importance  than  for 
boiler  use.  Here,  too,  the  soap  test  is  of  much  value,  since  those 
substances  which  will  precipitate  soap,  or  which  make  a  water 
"  hard,"  will  also  precipitate  rosin  size,  and  the  precipitate  formed 
will  have  quite  different  properties  from  that  formed  by  a  salt  of 
alumina  or  an  alum.  A  given  amount  of  size,  for  example,  will 
not  size  a  paper  nearly  so  hard  when  a  hard  water  is  employed  as 
it  will  with  a  soft  water.  Especially  will  this  be  the  case  when 
the  size  is  added  first  and  the  alum  later.  When  this  order  is 
followed,  the  size  may  even  be  entirely  precipitated  by  the  impur- 
ities of  the  water  before  the  alum  is  added,  and  the  alum  have  no 
effect  whatever.  In  a  case  of  this  kind,  a  little  soda-ash,  added 
before  the  size  and  alum,  will  help  the  matter  very  much. 

For  use  in  paper-making,  the  absence  of  organic  impurities,  and 
especially  of  such  as  impart  color  to  the  water,  is  of  great  impor- 
tance, both  in  tho  paper  machine  and  in  the  bleaching.  In  using 
a  colored  water  that  must  be  bleached  as  well  as  the  fibre,  it 
often  occurs  that  no  small  proportion  of  the  bleach  required  to 
bring  a  chest  or  an  engine  of  stock  u  up  to  color "  is  expended 
upon  the  organic  impurities  in  the  water. 

A  direct  test  of  the  amount  of  bleaching-powder,  or  available 
chlorine,  a  water  will  destroy  may  be  easily  made  by  adding  a 
measured  amount  of  bleaching-powder  solution  of  known  strength 
to  a  given  volume  of  the  water,  and  gently  warming  for  an 
hour,  and  then  determining  the  available  chlorine  remaining  by 
means  of  standard  arsenic  solution.  (Compare  determination  of 
strength  of  bleaching-powder,  under  Hypochlorites.)  The  dif- 
ference between  the  available  chlorine  added  and  that  remaining 


412  THE  CHEMISTRY  OF  PAPER-MAKING. 

in  the  water  will  be  the  amount  of  available  chlorine  destroyed 
by  the  amount  of  water  taken  for  the  experiment,  or  the  bleach- 
consuming  power  of  the  water. 

Boiler  Scales. 

These  are  ordinarily  residues  left  by  the  evaporation  of  the 
water  used  with  the  addition  of  iron  oxide  corroded  from  the 
boiler  shell,  and  sometimes  a  little  oil  which  has  found  its  way 
into  the  boiler.  The  presence  of  the  latter  may  be  recognized  by 
the  odor  on  heating  a  sample,  and  if  it  is  desired  the  amount  may 
be  determined  by  extracting  the  powdered  scale  with  ether  and 
weighing  the  oil  after  evaporation  of  the  ether.  The  analysis  of 
the  oil-free  residue  is  conducted  as  in  examination  of  water  residue 
(see  under  Water  Analysis). 

BISULPHITE   SOLUTIONS. 

The  bisulphite  solutions  are  chiefly  interesting  as  being  in  their 
several  forms  the  basis  of  all  the  processes  in  use  for  the  produc- 
tion of  "  Sulphite  Pulp  "  from  wood. 

The  oldest  of  these  processes  and  the  one  first  introduced  into 
this  country  by  Mr.  Charles  S.  Wheelwright  of  Providence,  R.T., 
:is  known  as  the  "Ekmann  Process"  and  employs  as  the  reduc- 
ing agent  a  solution  of  bisulphite  of  magnesium. 

Without  touching  on  the  at  present  disputed  point  whether  or 
not  the  bisulphites  of  the  earth  bases,  as  magnesia  and  lime,  really 
exist,  we  may  say  that  with  the  Ekmaun  process,  at  least,  it  has 
been  proved  by  experiment  that  a  solution  which  contains  sulphu- 
rous acid,  SO^,  and  magnesia,  MgO,  most  nearly  in  the  proportions 
theoretically  required  to  form  magnesium  bisulphite,  MgS2O6, 
gives  the  best  as  well  as  the  most  economical  results. 

Estimation  of  Sulphurous  Acid. 
Symbol,  SOr  —  Valency,  II.  —  Molecular  weight,  64. 

For  the  determination  of  the  total  sulphurous  acid,  SO2,  in  a 
solution,  we  require  a  standard  solution  of  iodine  and  some  starch 
paste. 

The  solution  of  iodine  is  prepared  by  weighing  accurately  12,7 
grammes  of  chemically  pure,  resublimed  iodine  on  a  watch-glass 


BISULPHITE  SOLUTIONS.  418 

and  transferring  the  same  to  a  flask.  About  18  grammes  roughly 
weighed  of  chemically  pure  potassium  iodide  is  added  to  the 
iodine  in  the  flask  and  about  100  c.c.  of  water.  The  whole  is  then 
allowed  to  rest  with  frequent  gentle  agitation  until  all  the  iodine 
i*  dissolved.  Heat  must  not  be  used  to  hasten  the  solution  of  the 
iodine,  and  the  flask  should  be  covered  or  fitted  with  a  glass 
stopper  and  kept  in  a  cool  place  during  solution.  When  the 
iodine  has  all  been  dissolved,  the  solution  is  to  be  diluted  to 
exactly  1000  o.c.  and  well  mixed.  This  will  form  a  ^-normal 
solution  of  iodine,  each  cubic  centimetre  of  which  is  equivalent  to 
0.0032  gramme  of  sulphurous  acid,  SO2.  The  strength  of  the 
solution  may  be  verified  by  means  of  the  standard  arsenic  solution 
mentioned  under  analysis  of  Hypoohiorites,  which  see.  The  two 
solutions,  if  strictly  deci-normal,  should  correspond  or  neutralize 
each  other  cubic  centimetre  for  cubic  centimetre. 

The  actual  determination  of  sulphurous  acid  is  made  as  follows, 
and  the  process  is  the  same  for  all  solutions  containing  sulphurous 
acid,  free  or.  combined  :  — 

The  specific  gravity  of  the  solutions  at  15°  C.  (60°  F.)  is  first 
ascertained. 

Next,  exactly  2  c.c.  of  the  solution  is  measured  and  diluted 
with  recently  boiled  water  to  about  100  c.c.  Two  or  three  grammes 
of  bicarbonate  of  soda  are  added  to  the  solution  and  a  few  drops  of 
thin  starch,  paste.  The  standard  iodine  solution  is  then  run  in 
gradually  with  constant  stirring  until  a  point  is  reached  where  the 
addition  of  a  single  drop  of  the  iodine  changes  the  entire  liquid 
from  colorless  to  a  blue  which  does  not  disappear  on  stirring. 

The  number  of  cubic  centimetres  of  iodine  solution  used  is  then 
read  off  from  the  burette.  This  number  of  cubic  centimetres, 
multiplied  by  0.0032,  the  value  in  SO3  of  one  cubic  centimetre* 
gives  the  grammes  of  SO2  contained  in  the  2  c.c.  of  the  solution 
used  for  the  experiment. 

In  order  to  calculate  this  figure  into  per  cents.,  we  must  take 
into  account  the  specific  gravity  of  the  solution  tested.  Suppose 
we  found  the  specific  gravity  to  be  1.0425,  then  the  2  c.c.  taken  for 
the  test  would  weigh  (1.0425x2)  2.085  grammes,  and  the  per 
centage  of  SO2  would  be  found  by  the  proportion  — 

2.085:  (SO2)  found  in  grammes •=  100 :  x  per  cents. 


414  THE  CHEMISTRY  OF  PAPER-MAKING. 

Determination  of  Sulphuric  Acid. , 
Reported  as  S03  —  Valency,  II.  —  Molecular  weight,  80. 

For  this  purpose  at  least  10  c.c*.  of  the  bisulphite  solution, 
accurately  measured,  are  placed  in  a  covered  beaker  and  an  excess 
of  strong  hydrochloric  acid  added  and  the  whole  boiled  for  some 
time,  the  object  of  boiling  with  excess  of  hydroenioric  acids  being 
to  free  the  solution  entirely  from  sulphurous  acid. 

For  this  purpose  more  than  enough  HC1  to  combine  with  all  the 
base  present  should  be  added  and  the  "boiling  continued  rapidly 
in  a  loosely  covered  beaker  until  no  smell  of  sulphurous  acid  is 
perceptible.  The  liquid  is  then  to  "be  diluted  to  about  100  c.c.,  and 
the  sulphuric  acid  precipitated  with  barium  chloride  solution,  as  in 
the  estimation  of  sulphuric  acid  in  Soda  Ash  (which  see),  being 
weighed  as  barium  sulphate. 

In  calculating  the  grammes  of  sulphuric  acid,  SOa.  formed, 
regard  must  be  had  to  the  specific  gravity  of  the  solution  tested,  as 
explained  under  determination  of  sulphurous  acid. 

Determination  of  Bases. 

In  the  determination  of  the  bases  in  "bisulphite  solutions,  atten- 
tion must  be  paid  to  the  presence  of  both  lime  and  magnesia,  even 
in  the  so-called  magnesia  liquors,  since  it  is  impossible  to  obtain 
magnesia  (as  raagnesite)  entirely  free  from  lime,  while,  on  the 
other  hand,  the  lime  used  for  making  bisulphite  of  lime  solutions 
always  carries  a  greater  or  less  proportion  of  magnesia. 

When,  as  is  sometimes  the  case,  soda-ash  is  used  in  connection 
with  lime  or  magnesia  in  making  the  liquors,  soda  is  also  present, 
which  complicates  the  matter  still  further. 

When  only  lime  and  magnesia  are  present,  it  is  sufficient,  in 
order  to  determine  the  amount  of  each,  first  to  convert  the  entire 
amount  of  both  the  lime  and  the  magnesia  into  sulphates  and 
obtain  the  weight  of  the  mixed  sulphates, 

For  this  purpose  it  is  only  necessary  to  measure  out  10  or  20 
c.c.  of  the  sample  with  a  pipette  into  a  platinum  dish  (por- 
celain may  be  used  if  care  is  taken  in  igniting),  add  sulphuric  acid 
in  slight  excess,  and  evaporate  to  dryness  over  the  water-bath. 
The  sulphuric  acid  will  combine  with  all  the  bases  present,  while 
the  sulphurous  acid  will  be  set  free  and  will  be  volatilized  with  the 


BISULPHITE  SOLUTIONS.  415 

water.  It  is  well  to  cover  the  dish  with  a  watch-glass  until  effer- 
vescence ceases.  It  may  then  be  removed,  rinsed  into  the  dish, 
and  the  evaporation  completed  without  fear  of  loss.  After  drying 
over  the  water-bath,  the  mass  in  the  dish  is  to  be  heated  over  the 
naked  flame,  cautiously  at  first,  to  avoid  spattering,  until  no  more 
fumes  of  sulphuric  acid  appear,  and  finally  to  a  full  red  heat. 
It  is  then  cooled  in  the  desiccator  and  weighed.  Deducting  the 
weight  of  the  empty  dish  leaves  the  weight  of  the  total  sulphates 
of  the  bases  present. 

It  is  absolutely  essential  that  white  fumes  of  SO3  should  appear 
on  ignition.  If  they  do  not  appear,  the  mass  must  be  again  mois- 
tened with  dilute  sulphuric  acid,  and  dried  and  ignited  a  second 
time.  The  ignited  mass  should  be  of  a  pure  white  color,  or  at  most, 
only  a  trifle  reddish  from  a  trace  of  iron  which  is  sometimes  present. 
The  ignited  sulphates  should  be  weighed  quickly,  since  sulphate 
of  magnesia  after  ignition  absorbs  water  rapidly  from  the  air, 
and  rapidly  increases  in  weight  from  that  cause  when  exposed 
to  the  air.  It  will  be  found  convenient  to  calculate  the  weight 
of  the  total  sulphates  of  the  bases  found  as  above  to  per  cents,  on 
the  weight  of  the  sample  as  explained  previously. 

In  order  to  separate  the  lime  and  magnesia  present,  the  mixed 
sulphates  obtained  as  above,  after  weighing,  are  treated  with  about 
5  c.c.  of  water  and  one  or  two  drops  of  hydrochloric  acid, 
breaking  down  any  lumps  in  the  mass  with  a  glass  rod.  This 
serves  to  dissolve  all  the  sulphate  of  magnesia,  together  with  a 
portion  of  the  sulphate  of  lime.  The  whole  is  then  rinsed  into 
a  beaker  by  the  aid  of  the  wash-bottle  and  the  smallest  possible 
amount  of  water ;  one  or  two  drops  of  strong  sulphuric  acid  added, 
and  strong  alcohol  equal  to  twice  the  volume  of  the  liquid  in  the 
beaker  poured  in.  The  whole  is  well  stirred  and  left  at  rest  for 
an  hour  or  longer.  It  is  then  to  be  filtered  and  the  precipitate 
washed  two  or  three  times  with  alcohol  of  60  per  cent,  strength 
to  remove  acid,  and  then  with  alcohol  of  40  per  cent,  strength  so 
long  as  the  latter  removes  anything.  This  latter  point  may  "be 
determined  by  evaporating  a  few  drops  of  the  filtrate  on  a  piece 
of  platinum  or  on  glass,  when  the  presence  of  any  residue  will 
indicate  that  the  washing  is  not  completed.  When  all  soluble 
matter  is  removed  by  the  40  per  cent,  alcohol,  the  precipitate 
remaining  on  the  filter  may  be  taken  as  pure  sulphate  of  lime, 
and  may  be  dried,  ignited,  and  weighed  as  such;  CaSO4.  The 


416  THE  CHEMISTRY  OF  PAPER-MAKING. 

weight  of  CaSO4  x  0.4118  gives  the  equivalent  lime,  CaO,  which 
may  be  calculated  to  per  cents,  on  the  original  sample.  The  weight 
of  the  sulphate  of  lirne  as  above  deducted  from  the  weight  of 
the  mixed  sulphates  found,  leaves  the  sulphate  of  magnesia, 
MgSO4,  which  x  0.3333  equals  magnesia,  MgO,  which  in  turn  is 
to  be  calculated  to  per  cents.  When  soda  is  present  as  well  as 
lime  and  magnesia,  the  best  mode  of  procedure  is  as  follows :  — 

First,  evaporate  10  c.e.,  or  a  larger  quantity,  to  dryness  over 
the  water-bath,  with  excess  of  hydrochloric  acid.  Take  up  the 
residue  with  a  few  drops  of  water,  and  transfer  to  a  beaker, 
rinsing  the  dish  with  as  little  water  as  practicable  to  insure 
the  removal  of  the  entire  substance.  Add  to  the  solution  in  the 
beaker  gradually,  with  constant  stirring,  a  slight  excess  of  strong 
sulphuric  acid,  and  then  strong  alcohol  equal  to  twice  the  bulk  of 
the  liquid.  Stir  well  and  allow  to  stand  for  an  hour  or  longer. 
This  will  precipitate  all  the  lime  as  sulphate,  which  is  to  be  washed 
on  a  filter  with  60  per  cent,  alcohol  to  remove  acid,  and  finally 
with  40  per  cent,  alcohol  to  remove  all  soluble  matter,  dried, 
ignited,  and  weighed  as  sulphate  of  lime,  CaSO4,  as  before. 

The  filtrate  from  the  CaSO4  precipitate  is  to  be  evaporated  to  a 
small  volume  over  the  water-bath  to  expel  the  alcohol.  It  is  then 
allowed  to  cool,  some  ammonium  chloride  solution  added,  and  a 
large  excess  of  ammonia,  and  finally  an  excess  of  phosphate  of 
soda  solution,  the  whole  well  stirred  without  touching  the  sides  or 
bottom  of  the  glass  with  the  stirrer,  and  allowed  to  rest  for  a 
couple  of  hours.  This  will  precipitate  the  magnesium  as  phos- 
phate of  magnesium  and  ammonia.  This  is  to  be  filtered  off  and 
washed  thoroughly  with  dilute  ammonia  (15  e.c.  of  strong  ammonia 
to  the  100  c.c.),  dried,  ignited  strongly,  and  weighed  as  magnesium 
pyrophosphate,  Mg3P2O7,  which  x  0.3604  gives  equivalent  mag- 
nesia, MgO. 

For  the  determination  of  soda,  10  e.c.  or  more  should  be 
placed  in  a  platinum  (or  porcelain)  dish,  and  baryta  water 
added  to  alkaline  reaction.  The  whole  is  then  to  be  evaporated 
nearly  to  dryness,  and  filtered  and  washed  thoroughly.  The  filtrate 
which  contains  all  the  soda  is  evaporated,  with  the  addition  of  a  few 
drops  of  ammonium  chloride  solution,  to  dryness  over  the  water- 
bath,  and  the  residue  gently  ignited,  not  to  fusion,  so  long  as  fumes 
of  ammonium  chloride  appear.  The  residue  is  dissolved  in  a  very 
little  water,  and  a  few  drops  (excess)  of  ammonium  oxalate  added 


ROSIN   SIZE.  417 


to  precipitate  the  excess  of  baryta  present  added.  The  solution 
is  to  be  again  filtered,  and  the  filtrate  evaporated  with  ammonium 
chloride,  *  and  ignited,  and  the  process  repeated  so  long  as  the 
solution  of  the  ignited  substance  continues  to  give  any  precipitate 
with  ammonium  oxalate  solution.  The  final  residue  will  consist 
of  pure  chloride  of  sodium,  which  is  to  be  weighed  after  ignition 
to  incipient  fusion  in  the  dish,  and  the  weight  of  the  dish  deducted. 

The  chloride  of  sodium,  NaCl,  formed  x  0.5306  gives  the  equiv- 
alent soda,  Na2O,  which  is  to  be  calculated  to  per  cents,  on  the 
original  sample,  as  previously  explained.  In  calculating  the  com- 
position of  a  bisulphite  liquor  from  the  results  of  analysis,  the 
sulphuric  acid  formed  is  always  combined  with  lime.  When  less 
than  enough  lime  to  saturate  the  sulphuric  acid  is  present,  the 
lime  present  is  first  saturated,  and  the  balance  of  the  SO3  calcu- 
lated to  sulphate  of  magnesia,  MgSO4. 

Excess  of  lime  over  that  required  to  combine  with  sulphuric 
acid  present  is  calculated  to  calcium  bisulphite,  CaS2O6,  since 
monosulphite  of  calcium,  CaSO3,  is  almost  entirely  insoluble. 
The  sulphurous  acid,  SO2,  still  remaining  goes  first  to  form  mono- 
sulphite  of  magnesia,  MgSO3,  and  any  excess  over  the  amotmt 
required  for  this  to  form  magnesium  bisulphite,  MgS2O5.  Any 
excess  of  SO2  over  the  amount  necessary  to  form  bisulphite  with 
all  the  lime  and  magnesia  present  is  counted  as  free  SO3  unless 
soda  is  present.  In  the  latter  case  it  'goes  first  to  form  sulphite  of 
soda,  Na2SO3,  and  second  to  form  bisulphite  of  soda,  NaHSO3. 
Any  excess  over  the  amount  necessary  to  form  bisulphite  with  the 
total  amount  of  all  the  bases  present  is  counted  as  free  SO2.  As 
we  have  said,  the  best  and  most  economical  liquor  is  that  in  which 
the  bases  and  sulphurous  acid  are  present  in  the  exact  proportions 
necessary  to  form  the  respective  bisulphites,  and  these  proportions 
can  only  vary  within  narrow  limits  without  causing  serious  losses 
both  in  the  manufacture  of  the  solution  and  in  the  quality  of  the 
pulp  produced,  as  well  as  serious  difficulties  both  with  the  liquor 
apparatus  and  with  the  digesters  employed. 

ROSIN   SIZE. 

Common  rosin  or  colophony  consists  for  the  most  part  of  a  mix- 
ture of  pinic  and  sylvic  acids  which,  when  boiled  with  soda-ash, 
gradually  combine  with  the  soda  to  form  pinate  and  sylvate  of  the 


418  THE  CHEMISTRY  OF  PAPER-MAKING. 

alkali,  or,  as  we  commonly  term  the  whole  compound,  resinate  of 
soda  or  rosin  soap. 

This  rosin  soap  in  a  semi-solid  state  forms  the  common  rosin 
size  of  the  paper  mill.  As  ordinarily  met  with  in  the  mills,  it 
contains  from  40  per  cent,  to  60  per  cent,  of  moisture.  The 
amount  in  a  given  sample  may  be  determined  by  drying  a  sample 
at  100°  C.  and  noting  the  loss  of  weight.  Rosin  soap  being  hard 
to  dry  in  a  mass,  a  convenient  mode  of  procedure  is  as  follows :  — 

The  sample  (about  5  grammes)  in  which  the  moisture  is  to  be 
determined  is  weighed  in  a  porcelain  dish.  It  is  then  dissolved  in 
the  smallest  possible  quantity  of  hot  alcohol  and  about  50  grammes 
of  sand  previously  dried  and  accurately  weighed  added.  The 
alcohol  may  then  be  evaporated  over  the  water-bath,  and  the 
residue  dried  in  the  water-oven  and  weighed. 

Free  Rosin. 

If  it  is  desired  to  estimate  the  free  rosin  in  a  rosin  size,  the 
sample,  about  5  to  10  grammes  of  the  thick  size,  should  be  first 
dissolved  iu  strong,  hot  alcohol  and  filtered.  This  will  give  in 
the  solution  all  the  rosin  free  and  combined  with  soda,  while  any 
excess  of  soda-ash  which  may  be  present,  as  well  as  other  impu- 
rities, such  as  sulphate  of  soda,  sand,  etc.,  will  remain  insoluble  in 
the  alcohol,  and  may  be  dried  and  weighed  after  thorough  wash- 
ing with  alcohol. 

The  solution  should  be  freed  from  alcohol  by  evaporation  over 
the  water-bath  and  the  residue  taken  up  with  50  to  100  c.c.  of 
water.  The  solution  is  next  transferred  to  a  separator,  which  con- 
sists  of  a  pear-shaped  or  cylindrical  glass  vessel  provided  with  a 
glass  cock  below  and  a  glass  stopper  in  the  top.  About  50  e.c. 
of  strong  ether  is  added,  and  the  whole  well  (though  not  too  vigor- 
ously) agitated,  and  the  two  liquids  allowed  to  separate  into  two  lay- 
ers ;  the  upper  of  the  two  layers  of  liquid  being  the  ether  which 
has  dissolved  out  the  free  rosin,  and  the  lower  aqueous  solution 
containing  all  the  combined  rosin.  The  aqueous  solution  is  to  be 
drawn-  off  as  closely  as  possible,  and  the  ether  solution  washed 
once  or  twice  with  a  small  quantity  of  cold  water.  It  is  then 
transferred  to  a  weighed  vessel  and  the  ether  allowed  to  evapo- 
rate, and  the  residue  heated  to  100°  C.  for  a  few  moments  to  drive 
off  traces  of  moisture,  cooled,  and  weighed. 


MOSIN  SIZE.  419 


A  white  size  may  carry  25  to  30  per  cent.,  or  even  more,  of  free 
rosin,  on  the  dry  basis,  while  a  good  brown  size  should  carry 
scarcely  any  free  rosin. 

The  amount  of  combined  rosin  may  be  readily  determined  by 
simply  returning  the  water  solution,  from  which  the  free  rosin  has 
been  removed  by  shaking  with  ether  as  above,  to  the  separator, 
adding  an  excess  of  dilute  sulphuric  acid,  which  serves  to  free  the 
rosin  from  combination,  and  again  washing  out  with  ether,  evapo- 
rating, and  weighing,  as  in  estimation  of  free  rosin. 


420 


THE  CHEMISTRY  OF  PAPER-MAKING. 


CHAPTER  IX. 

PAPER-TESTING. 

COMPARATIVELY  little  attention  has  been  paid  in  this  country 
to  the  chemical  and  microscopical  examination  of  papers,  although 
in  Germany  much  work  in  this  direction  has  been  done  by  Herz- 
berg,  Martens,  Hartig,  Weisner,  and  others  who  have  so  far  de- 
veloped their  methods  and  brought  their  results  into  line  with 
practical  work  that  paper-testing  is  now  one  of  the-  regular 
departments  of  the  Koniglichen  Mechanish-Technischen  Versuehs- 
Anstalt  at  Charlottenberg,  and  in  similar  institutions  at  Berlin 
and  elsewhere.  As  a  result  of  this  work,  official  specifications 
are  now  prepared  under  a  system  of  classification,  to  which  papers 
must  conform  to  be  regarded  as  Normal  Papers,  so-called.  Ac- 
cording to  their  composition  normal  papers  are  divided  into  four 


CLASS  I.  —  Paper  composed  entirely  of  rags,  and  with  2  per  cent,  of 

ash  as  a  maximum. 
CLASS  II.  —  Paper  composed  of  rags,  with  admixture  of  sulphite  pulp, 

straw,  or  esparto,  but  free  from  -ground  wood,  and  with  not  over 

5  per  cent,  of  ash. 
CLASS  III. —Paper  composed  of  various   fibres,  but  without  ground 

wood,  and  with  15  per  cent,  of  ash  as  a  maximum. 
CLASS  IV. — Paper  composed  of  various  fibres,  whatever  the  per  cent. 

of  ash. 
Each  paper  must  be  well  sized,  and  without  free  acid. 

Upon   the  basis   of  physical   character  there  is  the  following 
classification :  — 


CLASSES. 

l. 

2. 

3. 

4. 

6. 

6. 

a.  Mean  breaking  length  in  metres 

6000 

5000 

4000 

3000 

2000 

1000 

&'.  Mean  elasticity  (per  .cent,  of  stretch) 

4.5 

4.0 

a.6 

2.5 

2.0 

1.6 

c.   Resistance  to  rubbing 

6. 

6. 

5. 

4. 

3. 

1. 

PAPER-TESTING.  421 


While  these  classifications  ma)*"  be  useful  as  affording  a  means  for 
the  ready  statement  of  the  characteristics  of  a  paper,  it  is  impossible, 
in  our  opinion,  to  divide  papers  rigidly  into  a  few  classes  in  such 
a  manner  as  to  have  the  classification  a  direct  exponent  of  their 
value ;  and  there  is  always  danger  under  any  such  system  that, 
by  a  strict  adherence  to  it,  one  may  overlook  in  case  of  a  given 
paper  the  special  qualities  which  fit  it  for  a  given  use.  It  is 
nevertheless  true  that  these  German  methods  have  the  advantage 
of  giving  greater  definiteness  to  the  statement  of  the  factors  upon 
which  the  value  of  a  paper  depends,  and  leave  less  to  the  capriee 
or  personal  equation  of  the  buyers,  and  the  classification  may  be, 
disregarded  without  detracting  in  the  least  from  the  value  of  the 
methods  upon  which  it  depends.  We  shall,  therefore,  in  the 
course  of  the  ^present  chapter  consider  these  methods  somewhat 
in  detail. 

Big'ht  and  Wrong  Sides  of  Paper.  —  Nearly  all  papers,  except 
those  which  have  been  coated,  have  a  different  texture  or  surface 
upon  their  different  sides,  and  the  quality  of  printing  done  upon 
such  papers  depends  largely  upon  which  side  the  impression  is 
made.  In  hand-made  papers  the  wire  side  is  regarded  as  the  right 
side,  although  this  is  rather  an  anomaly,  since  the  best  impression 
is  obtained  upon  the  upper  side.  In  machine-made  papers  the 
reverse  is  the  case,  so  far  as  nomenclature  is  concerned,  and  the 
wire  side  is  properly  said  to  be  the  wrong  side.  It  may  usually, 
especially  in  wove  papers,  be  detected  by  the  small  diamond- 
shaped  depressions  due  to  the  wire,  and  called  the  wire  mark. 
The  roughest  side  is  not  invariably  the  wrong  side,  as,  for  instance, 
in  case  of  paper  for  crayon  and  chalk  drawing,  where  the  right 
side  is  the  roughest  one.  Upon  opening  a  ream  of  unfolded  or 
"  flat "  paper,  the  upper  side  is  the  right  one,  and  if  the  pape<r  is 
folded  into  quires,  it  is  right  side  out.  According  to  Parkinson, 
machine-made,  azure  laid,  yellow  wove,  or  blue  papers  are  usually 
darker  on  the  wrong  side,  while,  if  hand-made,  the  right  side,  so- 
called,  is  the  darker. 

Direction  in  which  Paper  came  from  the  Machine.  —  This 
is  sometimes  important,  especially  when  cutting  strips  to  deter- 
mine the  strength  of  paper,  since  the  sheet  is  always  stronger  in 
the  direction  in  which  it  came  from  the  machine  than  along  its 
width.  In  case  of  paper  made  upon  a  cylinder  machine,  this 
point  is  vory  easily  determined,  since  the  fibres  are  so  laid  in  such 


422 


THE  CHEMISTRY  OF  PAPER-MAKING. 


FIG.  89. 


a  paper  that  it  tears  in  a  straight  line  along  the  length  of  the 
machine,  and  in  an  irregular,  jagged  one  at  right  angles  to  the 
line  marking  this  direction.  The  direction  in  which  a  machine- 
made  paper  was  run  off,  may  be  found  by  cutting  from  the  sheet 
a  circular  piece  about  10  cm.  in  diameter, 
floating  this  upon  water  for  a  few  seconds, 
and  then  raising  it  carefully  and  placing 
upon  the  palm  of  the  hand.  The  disc  will 
begin  to  curl,  until  finally  the  opposite  edges 
meet,  forming  a  sort  of  tube.  The  direction 
of  the  axis  of  this  tube  or  cylinder  gives 
the  direction  in  which  the  paper  came  from 
the  machine.  If  water-leaf  or  unsized  paper 
is  taken  for  the  test,  it  must  first  be  dipped 
in  a  weak  solution  of  rosin  in  absolute  alco- 
hol, and  dried  before  placing  in  the  water. 

Another  and  simpler  method  for  determining  this  direction  is 
to  cut  one  strip  about  one-half  an  inch  in  width  and  four  inches 
long  from  the  paper  lengthwise  of  the  sheet,  and  a  similar  strip 
across  the  sheet.  The  strips  should  be  marked  when  cut.  If 
when  held  at  one  end  by  the  thumb  and  forefinger,  as  shown  in 
Fig.  89,  the  strips  remain  closely  together,  as  there  shown,  the 
lower  strip  came  from  tha  direction  in  which  the  paper  was  run 
off.  If  the  strips  fall  apart,  as  in  Fig.  90, 
the  upper  strip  is  the  one  which  shows  this 
direction. 

Water  Marks.  —  An  examination  of  the 
water  marks  and  the  size  and  character  of 
the  wire  marks  is  sometimes  of  the  first  im- 
portance in  establishing  the  age  or  identity  of 
a  sample  of  paper,  but  the  inferences  drawn 
from  such  inspection  are  not  always  conclu- 
sive. It  is,  of  course,  not  a  difficult  matter 
to  imitate  a  water  mark,  and  we  have  seen 
samples  in  which  not  only  the  marks,  but  the 
characteristics  of  the  stock,  and  even  of  the  dirt  observed  in 
ancient  papers,  were  closely  reproduced.  Many  designs  having 
the  appearance  of  a  water  mark,  and  which  are  in  some  cases 
of  high  artistic  merit,  are  now  produced  in  paper  by  subjecting 
the  sheet  to  heavy  pressure  under  a  die.  Legitimate  water 


FIG.  90. 


PAPER-TESTING.  428 


marks  may,  in  tins  way,  be  closely  imitated,  so  that  occasions 
may  arise  when  it  becomes  important  to  determine  the  manner 
in  which  the  marks  were  made.  The  true  watt*  mark  made 
by  the  dandy-roll,  or  by  wires  on  the  bottom  of  the  mold,  is 
thinner  than  the  rest  of  the  sheet,  for  the  reason  that  there  is 
actually  less  material  where  the  lines  occur  than  would  be  the 
case  if  they  were  absent.  The  spurious  mark  is  thinner,  merely 
because  the  material  has  been  compressed;  the  lines  contain  as 
much  fibre  as  any  similar  portion  of  the  paper.  Wetting  the 
paper  with  strong  caustic  soda  solution,  therefore,  renders  the  true 
mark  more  conspicuous,  but  obliterates  the  spurious  one. 

Finish  and  Evenness  of  Sheet.  —  There  is  no  method  of  mak- 
ing a  quantitative  estimate  of  either  of  these  factors  which  have 
so  important  a  bearing  in  determining  the  market  value  of  papery 
and  one  can  only  gain  the  needful  accuracy  of  judgment  by  the 
study  and  comparison  of  many  different  sheets  with  reference  to 
their  intended  use.  In  general,  smoothness  and  evenness  of  tex- 
ture are  more  desirable  in  book  papers  than  an  extremely  high  gloss, 
which  is  apt  to  be  trying  to  the  eyes. 

Papers  in  which  the  fibre  is  long  and  has  been  little  beaten  are 
usually  rather  uneven  or  "wild,"  as  will  be  noticed  on  holding 
them  to  the  light.  In  such  papers  the  finish  is  '.higher  on  the 
thicker  portions,  and  on  looking  across  them  at  the  light  appears 
blotchy  and  uneven.  This  is  a  frequent  characteristic  of  all-sul- 
phite paper,  and  if  unbleached  sulphite  has  been  used,  the  effect  is 
heightened  by  the  natural  gloss  of  the  hard  fibre.  A  "hairy  "  look, 
due  to  the  projection  of  the  ends  of  fibres  from  the  surface,  is 
objectionable,  as  is  also  any  tendency  for'the  filler  to  leave  the 
paper  as  "dust."  .This  is  noticed  upon  •  drawing  the  paper  over  a 
black  coat-sleeve, -and  causes  trouble  in  sprinting,  by  clogging  and 
filling  the  type,  and  especially  the  fine  lines  of  process  cuts. 

IMrt.  —  The  common  way  of  detecting  dirt  in  paper  is  by  hold- 
ing the  sheet  to  the  light ;  but  this  method  is  not  altogether  fair 
to  the  paper-maker,  since  in  use  it  is.  generally  only  .the  surface  dirt 
which  shows  or  is  objectionable.  This  surface  dirt  may  be  brought 
into  prominence  by  drawing  a  small  circle  around  the  larger  specks. 
In  this  way  the  comparative  cleanness  of  two  or  more  sheets  for 
the  purposes  of  practical  work  may  be  determined  at  a  glance. 
The  character  of  the  dirt  is  of  more  importance  to  the  paper-maker 
tjian  to  the  consumer.  Shive  and  lumps  of  fibre  are  usually 


424  THE  CHEMISTRY  OF  PAPER-MAKING. 

detected  at  once  by  their  comparatively  large  size  and  general 
appearance.  If  due  to  uncooked  wood,  their  color  is  intensified 
by  a  drop  of  aniline  sulphate  solution.  Slime  marks  and  size  spots 
are  more  or  less  transparent,  and  if  large,  break  the  continuity  of 
the  sheet.  Fine  particles  of  iron  from  the  engine  rolls  are  far 
more  numerous  in  paper  than  is  commonly  supposed.  They  may 
be  distinguished  from  other  dirt  by  moistening  the  paper  with  very 
weak  hydrochloric  acid,  then  allowing  it  to  dry  and  dipping  in  a 
weak  solution  of  ferrocyanide  of  potash.  Each  bit  of  iron  then 
stands  out  surrounded  by  a  blue  zone.  Spots  due  to  filler  or  to 
calcium  sulphite  derived  from  sulphite  pulp  are  usually  nearly 
white,  and  break  up  under  the  point  of  a  -pin  into  many  smaller 
particles.  Mica  in  the  filler  is  perhaps  not  properly  dirt,  but  is 
equally  noticeable  from  its  shiny  appearance,  which  causes  it  to 
stand  out  upon  the  surface. 

Other  dirt  may  consist  of  bits  of  bark  or  leaves  or  other  vege- 
table matter  derived  from  the  water  or  the  pulp.  Particles  of  coal, 
tiny  fragments  of  copper,  and  many  other  things  find  their  way 
into  the  paper,  either  from  the  air  or  more  commonly  from  the 
stock  or  chemicals.  Their  exact  nature  can  usually  be  determined 
by  simple  chemical  tests  or  by  a  microscopical  examination,  and 
not  infrequently  their  source  may  be  thus  pointed  out. 

Mechanical  Testing:  Thickness.  —  This  is  determined  by  means 
of  an  ordinary  screw  micrometer  gauge  with  divisions  giving  thou- 
sandths of  an  inch,  while-  the"  spaces  between  divisions  may  be  read 
to  one  or  two  ten-thousandths.  The  ends  of  the  micrometer  which 
touch  the  paper  should  have  rather  wide  disks  or  flanges,  and  care 
must  be  taken  not  to  compress  the  paper  in  bringing  them  down 
upon  it.  It  is  often  important  to  compare  papers  Avith  reference  to 
their  so-called  "  thickness  for  weight."  A  direct  numerical  com- 
parison may  be  made  by  first  figuring  the  weights  of  the  papers  into 
sheets  or  reams  of  equal  size  and  dividing  the  weight  of  each  by 
the  thickness  in  ten-thousandths  of  an  inch.  The  weights  of  equal 
thicknesses  of  the  papers  are  then  directly  proportional  to  the 
quotients  obtained.  Where  other  things  are  equal,  laid  papers  are 
always  thicker  for  weight  than  wove. 

Mechanical  Testing:  Strength  and  Stretch.  —  The  strength  of  a 
paper  is  the  quality  to  which  attention  is  usually  first  directed  if  its 
general  appearance  is  in  any  way  satisfactory.  It  is  usually  deter- 
mined in  this  country  either  very  roughly  by  tearing  or  inore  accu- 


PAPER  TESTING. 


425 


lately  by  testing-machines  which  give  only  relative  results  useful 
for  direct  comparisons.  The  stretch  which  is  of  especial  importance 
in  papers  .used  for  lithographic  work  or  for  other  purposes  for  which 
an  accurate  register  is  necessary  is  not  determined  at  all.  Several 
paper-testing  machines  which  give  both  the  strength  and  stretch  of 
paper  in  absolute  terms  which  permit  of  strict  comparison  without 
reference  to  the  width  or  thickness  of  the  samples  are  now  in  com- 
mon use  in  Europe,  and  will  be  noted  in  some  detail.  The  one 
which  has  found  most  general  introduction  in  the  institutions  de- 
voted to  paper-testing  is  the  Wendler  apparatus  shown  in  Fig.  91. 
To  obtain  accurate  information  about  the  quality  of  paper  with 
respect  to  strength  and  stretch,  a  strip  of  definite  length  and  width 
is  cut  from  the  sheet,  and  is  then  strained  either  by  weights  or  a 
spring  of  known  strength,  until  it  breaks.  The  measure  of  the 
strain  gives  the  fracture  weight,  and  the  stretch  of  the  strip  up 
to  the  point  of  fracture  is  called  the  fracture  stretch.  For  com- 
plete data,  the  paper  should  be  thus  tested  both  with  the*  length 
of  the  machine  and  across  it,  since  both  the  strength  and  elasticity 
of  the  paper  vary  with  the  direction  in  which  the  strip  is  cut. 
The  power  needed  to  tear  the  strip  is  no  criterion  of  the  strength 
of  the  stock  from  which  the  paper  is  made,  as  it  gives  merely  the 
strength  with  which  the  fibres  have  felted,  and  varies  also  with 
thickness  of  the  sheet.  The  strength  of  paper  is  expressed  in 
Germany  in  terms  of  fracture  length,  the  fracture  length  being  the 
length  of  a  strip  of  any  width  or  thickness,  which,  if  suspended  by 
its  upper  end,  would  have  just  weight  enough  to  cause  the  strip  to 
break.  The  following' example  will  show  the  method  of  calculat- 
ing the  fracture  length.  Ten  strips  were  cut  from  the  sheet,  five 
being  with  the  length  of  the  machine  and  five  across  it:  — 


WITH  THE  LENGTH. 


ACBOS8  THE  MACHINE. 


Fracture  Strength. 

Fracture  Stretch. 

Fracture  Strength. 

Fracture  Stretch. 

1. 

2. 
3. 

4. 
6. 

17.56  Ibs. 
17,44     « 
17.36    ^ 
17.40     " 
17.60    *> 

1.9  per  cent. 
1.8        " 

".'    1.8 
1.8        " 
1.9         " 

1. 
2. 
3. 
4. 

5. 

10.  80  Ibs. 
10.88    " 
10.60    «» 
10.76    «' 
10.80    ** 

3.6  per  cent. 
3.6 
3.4        «' 
3.5        «* 
3.5        4t 

87.36  Ibs. 
Avg  17.47   " 

9.2  per  cent. 
1.84      " 

53.84    fts. 
Avg.,.   10.7G3    *' 

17.6   per  cent. 
3.52      ' 

426  THE  CHEMISTRY  OF  PAPER-MAKING. 

These  tests  were  made  on  the  Wendler  apparatus*  and  their 
close  agreement  will  be  noticed.  The  average  weight  of  the  strips 
was  0.0151  ounces,  and  in  order  to  figure  the  fracture  lengths, 
one  has  to  determine  the  length  of  the  strips  of  the  same  width 
which  will  weigh  17.47  Ibs.  and  10.768  Ibs.  respectively.  Calling 
the  unknown  length  in  the  first  case  #,  the  length  of  the  strip 
taken  being  9  inches,  we  have  the  proportion  :  — 

|  ft.  :  0.0151  oz.  »  x  :  279.52  oz. 

-*»»*• 


Across  the  machine  we  have  10.768  Ibs.,  or  172.280  ounces 
fracture  strength  ;  therefore  — 

f  ft.  :  0.0151  oz.  =  x  :  172.288. 
gasLxl72:288 
0.0151 

Our  data  may,  therefore,  be  summed  up  as  follows  :  — 

With  the  length  .     .     .  13884  ft.  fract  length.  1.84  per  cent,  stretch. 

Across  the  machine      .     8557  ft.  fract.  length.  3.52  per  cent,  stretch. 

22441  ft.  5^  per  cent. 

Average   .....     11220ft.  2.68        " 

Upon  these  figures  the  paper  is  classified  in  the  official 
schedules.  The  calculation  is  'greatly  simplified  by  tables  con- 
taining what  are  known  in  Germany  as  fineness  numbers  ;  that  is, 
the  quotients  obtained  by  dividing  the  length  of  the  strip  by  its 
weight.  From  these  tables  the  number  by  which  we  should 
multiply  the  fracture  weight  in  order  to  get  the  fracture  length, 
can  be  at  once  obtained.  Such  well-known  authorities  as  A. 
Martens,  superintendent  of  the  Berlin  Royal  Testing  Institution, 
Professor  Hartig,  Professor  Weisner,  and  W.  Herzberg,  have 
already,  as  has  been  stated,  done  mvich  toward  the  classification  of 
German  papers,  and  the  determination  by  this  method  of  the 
influence  of  air,  light,  water,  acids,  sizing,  and  pressure  upon  the 
quality  of  paper. 

The  Wendler  apparatus  consists  essentially  of  four  main  parts  :  —  • 

1.  The  actuating  mechanism. 

2.  The  arrangement  for  holding  the  strip. 

3.  The  spring. 

4.  The  mechanism  for  measuring  the  strength  and  stretch. 


PAPER-TESTING. 


427 


The  first  consists  of  a  hand  wheel,  E,  or  a  worm,  F.  The  top 
of  the  wheel  turns  in  the  bearing  block,  which  is  cast  in  one  piece 
with  the  bed.  The  screw  H  is  tight  with  the  sled  JT,  and  is  led 
through  the  nut  <?,  which  consists  of  a  shell  containing  a  clutch 
which  may  be  thrown  in  or  out  by  turning  the  nut  about  90°. 

The  arrangement  for  holding  the  strip  consists  of  two  clamps,  d 
and  /,  the  first  being  connected  with  the  spring  and  the  other 
with  the  sled.  The  strip  is  put  between  the  jaws  of  the  clamps, 
which  are  then  pressed  together  by  screws. 

Two  springs  may  be  used,  one  of  20  Ibs.  strength,  and  the 
other  of  40  Ibs.,  the  latter  for  heavy  papers.  The  spring  is 


Fig.  91.  —  WENDLER  PAPER-TESTING  APPARATUS. 

supported  at  one  end  by  the  bed,  and  at  the  other  end .  by  the 
movable  carriage.  The  rack  is  connected  with  the  carriage  and 
passes  through  the  shell  to  the  rear  of  the  spring,  where  there 
are  pawls  which  catch  in  the  teeth  of  the  rack  and  prevent  the 
spring  from  flying  back  when  the  paper  breaks. 

The  strain  is  measured  as  follows :  The  carriage  pushes  the 
indicator  before  itself  by  means  of  an  angle  rod.  The  indicator 
has  a  zero  mark,  under  which  is  read  on  the  &cale  the  fracture 
strength  after  the  strip  breaks.  The  stretch  is  shown  in  per  cents, 
of  length  by  another  indicator  attached  to  the  sled  K.  The  scale 
above,  which  this  indicator  moves,  goes  forward  at  the  same  rate 


428  THE  CHEMISTRY  OF  PAPER-MAKING. 

as  the  carriage,  while,  if  the  paper  stretches,  the  indicator  moves 
forward  enough  faster  to  take  up  the  stretch,  and  from  its  position 
at  the  end  of  the  test  the  stretch  is  read  directly. 

To  test  a  paper  with  this  apparatus,  the  strength  scale  is 
adjusted  by  raising  the  pawls  «,  bringing  the  indicator  up  against 
the  angle  rod,  and  the  zero  marks  on  scale  and  indicator  together. 
Spring  It  is  held  in  position  by  the  screw  /,  which  is  tightened  for 
the  purpose.  A  strip  of  the  paper  to  be  tested  is  placed  between 
the  clamps  /  and  dj  the  clutch  G-  is  thrown  in,  and  the  screw  I 
loosened  to  free  the  spring,  then  by  the  hand,  or  better,  by  a  little 
water  or  electric  motor,  the  wheel  E  is  slowly  turned  until  the 
paper  breaks.  After  tearing  the  strip  the  breaking  strain  and 
stretch  are  read  from  the  scales,  and  the  spring  is  made  to  resume 
its  normal  position  by  raising  the  pawls  s  and  slowly  letting  the 
carriage  back* 

Thft  Schopper  Testing-Machine.  —  In  using  this  machine,  the 
samples  required  for  testing  have  first  to  be  prepared.  This  is 
done  as  follows:  A  piece  of  the  sheet  is  taken  and  cut  to  a 
length  of  12  inches,  and  then  cut  off  in  strips  by  the  cutting  blade, 
fixed  upbn  the  scale.  The  sheet  of  paper,  when  the  correct 
length  is  once  obtained,  is  simply  put  under  the  knife  and  rested 
against  an  edge,  beyond  which  it  cannot  go.  The  knife  is  then 
lowered,  thereby  cutting  off  the  strip  to  the  needful  size.  Some 
little  care  is  naturally  required  to  see  that  this  cutting  of  the 
paper  is  properly  accomplished  with  due  accuracy  as  to  width. 
This  the  cutter  arranges  automatically,  if  carefully  and  methodi- 
cally handled.  After,  say,  ten  or  a  dozen  strips  are  cut  off  the 
sample,  they  are  numbered  in  Iqad  pencil  from  one  to  ten,  or 
alphabetically,  and  the  position  in  the  sheet  whence  they  come  is 
also  noted  down  on  each  strip.  After  having  correctly  obtained 
two  sets  of  strips,  one  set  across,  and  the  other  along  the  direction 
of  the  paper  as  it  came  from  the  machine,  and  each  having  been 
marked,  they  are  next  hung  upon  an  ordinary  paper  scale,  and 
the  weight  of  each  slip  is  taken  arid  multiplied  by  two,  which 
gives  the  equivalent  weiglit  of  this  sample  of  paper  as  a  ream. 
It  is  then  advisable  to  note  down  this  figure  upon  the  slip,  and 
also,  for  safety  sake,  upon  a  separate  sheet  of  paper.  As  soon  as 
the  weights  equivalent  to  a  ream  have  been  duly  noted,  the 
samples  are  ready  for  testing. 

The  apparatus  consists  of  a  levelling  stand,  upon  which 


PAPER-TESTING. 


429 


is  a  rod  or  pillar;  near  the  top  of  the  pillar  there  are  two  levers 
pivoted,  the  shorter  and  upper  portions  are  curved  or  bent  to  facil- 
itate the  attaching  of  other  parts  thereto,  and  t]ie  lower  or  longer 
arms  are  each  provided  with  an  index  pointer,  so  that  when  the 
material  is  being  tested  they  each  traverse  graduated  arcs.  One 
of  these  arcs  is  .fixed  to  the  pillar  and  is  graduated  to  indicate  the 
pull  exerted  at  the  shorter  end  of  the  lever.  The  other  arc  is 
attached  to  the  weight-indicating  lever,  and  is  graduated  to  show 


Tig.  92.  —  SHOPPER   PAPER-TESTING   MACHINE. 

the  per  cent,  of  stretching  prior  to1  fracture  by  the  breaking 
weight. 

The  weight-indicating  arc  is  provided  with  ratchet  teeth,  and 
the  lever  with  a  series  of  pawls,  so  arranged  that  each  tooth  of 
the  ratchet  under  the  pawls  is  practically  divided  into  fractional 
parts,  thus  securing  strong  teeth  and  avoiding  shock  by  recoil 
when  the  paper  breaks. 

The  bent  or  shorter  arms  of  the  lever  have  suitably  pivoted 
connections.  In  case  of  the  tension  lever,  or  rod,  the  other  end 


430  THE  CHEMISTRY  OF  PAPER-MAKING. 

of  which  is  connected  with  a  slide,  the  weight  lever  has  a  clamp 
for  the  purpose  of  securing  one  end  of  the  paper  to  be  tested ;  the 
clamp  for  the  other  end  is  connected  with  the  slide  alluded  to 
above ;  the  slide  is  actuated  with  a  screw,  further  connected  with 
limit  cog  wheels  and  with  hand-driving  wheel*  to  communicate 
steady,  continuous,  slow  motion  to  the  slide. 

To  make  the  test,  a  definite  length  (according  to  the  graduation 
of  the  tension  arc)  of  paper  is  fixed  between  the  clamps,  in  its 
normal  straight  condition,  the  index  pointers  adjusted  to  zero 
by  means  provided,  then  the  wheel  turned.  The  screw  brings 
the  slide  down,  stretching  the  paper  until  it  breaks,  then  one  of 
the  series  of  pawls  prevents  recoil,  and  tne  breaking  weight  and 
tension  can  be  read  off. 

The  machine  must  stand  level,  and  this  can  easily  be  arranged 
by  ascertaining  that  the  weight  hangs  true,  and  that  the  index 
pointer  is  exactly  over  the  proper  mark  upon  the  curved  scale 
board.  Having  settled  this  matter,  and  fixed  the  weight  by 
inserting  a  small  pin  which  rests  in  the  stand,  the  wheel  is  duly 
set  at  its  limit,  and  the  screw  controlling  the  tension  rod  is 
fastened.  The  sample  slip  is  then  inserted  into  the  lower  clamp 
and  fastened  thereby.  This  is  very  simply  done,  by  merely  bend- 
ing the  clamp  back,  and  this  causes  the  paper  slip  to  become 
firmly  held,.  The  same  is  then  arranged  with  the  upper  clamp, 
the  slip  of  paper  being  gently  but  properly  held  taut  by  the  two 
clamps. 

All  being  ready,  the  pin  holding  the  weight  is  withdrawn,  and 
while  the  small  wheel  is  set  slowly  revolving,  the  screw  control- 
ling the  tension  rod  is  unfastened.  The  weight  at  onee  begins  to 
ascend  the  curved  scale  board,  passing  the  numbered  graduations 
en  route.  The  back  of  the  weight  is  provided  with  a  set  of  four 
separate  small  pawls,  which,  as  the  weight  ascends  the  scale  board, 
move  with  it  and  drop  into  ratchet  teeth  in  such  a  way  that  when 
the  sample  breaks  the  pawls  stay  the  weight  by  their  inability  to 
move  out  of  the  teeth.  The  figure  at  which  the  weight  drops  is 
indicated  by  the  pointer  and  denotes  the  number  of  pounds  which 
represent  the  force  of  the  strain.  Mean  while,  above  this  pointer, 
and  upon  a  smaller  scale  board,  another  pointer  has  been  moving, 
and  this  indicates  the  tension  of  the  sample,  or  the  amount  of 
stretch  per  cent,  of  which  the  sample  is  capable.  This  indicator 
also  stops  when  the  paper  breaks,  thereby  permitting  a  perfectly 


PA  PK&-TE8TING.  431 


accurate  reading  to  be  taken.  As  soon  as  this  has  been  done,  the 
small  ratchet  teeth  are  raised  and  the  weight  replaced  in  its 
primary  position  :  the  same  is  also  done  with  the  tension  pointer, 
which,  however,  is  without  any  ratchet  teeth  to  control  its  move- 
ment. 

The  Rubbing  Test.  —  The  extent  to  which  a  paper  will  bear 
folding  and  rubbing  without  breaking  has  in  many  cases  a  con- 
siderable influence  in  determining  its  value.  It  may  be  tested  in 
this  respect  by  crumpling  a  half  sheet  strongly  in  the  hand  to 
form  a  sort  of  ball,  then  smoothing  the  paper  and  repeating  the 
operation  several  times.  Papers  which,  with  reference  to  their 
power  of  resisting  wear,  would  be  classified  as  "  extremely  poor  " 
on  the  following  scale,  which  is  that  adopted  by  the  Germans,  soon 
develop  holes  under  this  treatment.  As  the  paper  succumbs  to, 
or  withstands,  this  treatment,  or  requires  in  addition,  in  order  to 
make  holes,  more  or  less  violent  rubbing  upon  itself  between  the 
hands,  it  is  given  a  number  which  has  the  significance  shown 
below :  — 

0.  Extremely  poor. 

1.  Very  poor. 

2.  Poor. 

3.  Medium. 

4.  Bather  good  quality. 

5.  Good  quality. 

6.  Very  good  quality. 

7.  Extremely  good  quality. 

News  and  similar  papers  would  be  marked  0,  while  a  Japanese 
or  very  strong  pure  jute  paper  would  be  given  the  number  7. 

Determination  of  Size.  —  The  methods  employed  in  the 
laboratory  of  the  Koniglichen  Mechanish-Technisehen  Versuchs- 
Anstalt  at  Charlo  It  anbury,  and  which  have  been  adopted  with 
slight  modification  in  our  own  laboratory,  are  thus  described  by 
Herzberg  and  others :  — 

The  test  for  animal  size  with  tannic  acid  depends  on  the  for- 
mation of  a  precipitate  of  tannate  of  gelatine.  When  tannic  acid 
is  added  to  a  solution  of  gelatine  which  is  not  too  dilute,  there 
will  be  formed  a  thick  gelatinous  precipitate.  In  a  very  dilute 
solution  only  a  milky  cloud  will,  be  seen,  which  will,  after  a  short 
time,  separate  in  flocks ;  the  cloudy  appearance  without  the 
separation  of  flocks  shows  the  absence  of  animal  size.  In  carrying 


432  THE  CHEMISTRY  OF  PAPER-MAKING. 


out  the  test  the  paper  is  first  treated,  as  described  above,  with 
distilled  water,  and  the  liquid  concentrated  as  much  as  possible 
by  evaporation,  as  then  it  is  easier  to  see  the  reaction.  When  the 
solution  is  cold,  a  concentrated  solution  of  tannic  acid  in  water  is 
added,  and  care  must  be  taken  to  observe  whether  a  precipitation 
and  separation  of  flocks  takes  place. 

When  either  very  small  amounts  of  material  are  available,  as  in 
the  case  of  old  manuscripts,  or  where  it  is  necessary  to  determine 
the  presence  of  very  small  quantities  of  animal  size,  this  method 
cannot  be  used,  and  the  reagent  of  Millon  is  alone  available  for 
the  purpose.  This  reagent  is  a  very  delicate  test  for  albumen,  a 
substance  always  present  in  animal  size,  and  is  prepared  as  fol- 
lows: To  a  weighed  quantity  of  metallic  quicksilver  an  equal 
weight  of  fuming  nitric  acid  is  added,  and  the  whole  allowed  to 
stand  in  a  cold  place  for  a  few  hours ;  after  which  an  equal  vol- 
ume of  distilled  water  is  added,  and  the  whole  left  quiet  for 
twenty-four  hours.  Prepared  in  this  way  the  reagent  will  keep 
active  for  about  four  weeks. 

A  small  piece  of  the  paper  to  be  tested  is  placed  on  a  watch- 
glass  and  moistened  with  the  reagent,  and  then  brought  on  to  a 
wire  gauze  and  heated  very  gradually.  If  animal  size  is  present, 
in  a  few  minutes  the  paper  will  be  colored  red ;  the  color  will* 
vary  from  rose  to  scarlet,  according  to  the  quantity  of  size  which 
is  present.  As  the  red  color  gradually  beoomes  brown,  it  is 
necessary  to  watch  the  paper  during  the  whole  reaction.  The 
coloration  can  also  be  seen  in  the  cold,  but  only  after  the  reagent 
has  acted  for  a  considerable  time  on  the  paper,  and  the  coloration 
will  never  be  so  distinct  as  when  the  paper  is  heated.  It  will  be 
found  advantageous  to  moisten  a  sample  of  the  paper  to  be  tested 
with  distilled  water,  and  to  treat  this  in  the  same  way  as  that 
moistened  with  the  reagent,  so  as  to  compare  the  resulting  colors. 
The  reagent  of  Millon  shows  the  presence  of  aromatic  groups 
containing  a  simple  hydroxyl;  this  being  present  in  albuminoid 
bodies,  it  is  consequently  a  test  for  albumen.  As  commercial  glue 
always  contains  albumen  (as  does  even  the  finest  colorless  gela- 
tine), the  reagent  may  be  used  as  a  test  for  animal  size.  However, 
it  must  be  noted  that  chemically  pure  gelatine  does  not  contain 
this  group ;  for  practical  purposes,  however,  this  is  of  no  conse- 
quence, but  the  presence  of  animal  size,  as  found  by  Millon's 


PAPER-TESTING.  433 


reagent,  can  only  be  considered  as  final  under  the  following  sup- 
positions :  — 

1.  That  the  paper  does  not  contain  albumen  as  such. 

2.  That  there  are  no  free  aromatic  groups  with  hydroxyl. 

With  regard  to  1.  Albuminoid  bodies  are  very  rarely  found  in 
paper  fibres  apart  from  size,  and  then  only  as  traces.  Further 
microscopical  research  will  show  whether  the  fibres  give  the 
albumen  reaction,  as  in  this  case  the  coloration  will  be  in  the 
central  canal  of  the  cell,  while  the  glue  remains  on  the  out- 
side of  the  fibre.  We  need  not  take  into  consideration  those 
cases  in  which  the  albumen  has  been  added  to  the  paper  for 
special  purposes,  as  in  albumenized  paper  for  photography.  As 
regards  the  second  supposition,  it  may  be  remarked  that,  apart 
from  vanilline,  we  do  not  expect  to  find  the  foremen tiofted  aro- 
matic groups  in  paper.  If  vanilline  is  present  as  a  compound  of 
wood,  it  can  be  found  by  phloroglucin  and  hydrochloric  acid, 
which  enables  us  to  determine  its  origin.  If  the  gelatine  used  for 
sizing  is  already  decomposed,  Millon's  reagent  will  no  longer  show 
it.  In  testing  old  writing  material,  where  fine  parchment  having 
the  greatest  similarity  to  paper  is  often  found,  it  is  also  necessary 
to  take  the  fibres  into  consideration;  such  parchment  will,  of 
course,  at  once  be  affected  by  Millon's  reagent,  not  because  it  hae 
been  sized,  but  because  it  consists  of  substances  containing 
gelatine. 

As  to  whether  the  active  sizing  material  in  rosin  size  is  free 
rosin,  resinate  of  alumina,  or  a  mixture  of  both,  opinions  are  as 
yet  divided*  While  Wiirster  considers  that  the  sizing  of  paper 
is  caused  by  free  rosin  only,  Tedesco  and  Rudel  think  that  the 
active  principle  is  a  compound  of  rosin  and  alumina.  That  under 
all  circumstances  free  rosin  is  present  in  rosin-sized  paper,  cannot 
be  doubted,  and  indeed  the  test  described  below  for  rosin-sized 
paper  depends  on  this. 

Half  a  sheet  of  the  paper  to  be  tested  is  torn  up  into  small 
pieces  and  absolute  ak.ohol  poured  onto  it ;  the  vessel  containing 
it  is  stood  in  hot  water  for  about  half  an  hour.  When  rosin  is 
present,  it  is  easily  dissolved  out  by  the  alcohol,  as  is  also  resinate 
of  alumina  to  some  extent.  If  this  solution  is  poured  into  a  suffi- 
cient quantity  of  cold  water,  the  rosin  will  be  precipitated,  as  the 
dilute  alcohol  cannot  dissolve  it.  The  distilled  water  will  assume 


434  THE  CHEMISTRY   OF  PAPER-MAKING. 

a  milky  appearance*  the  intensity  of  which  will  depend  on  the 
quantity  of  rosin  present. 

In  the  method  described  by  Schuman,  a  weighed  quantity  of 
paper  is  cut  into  the  smallest  pieces  possible  and  warmed  for  a 
considerable  time  in  a  porcelain  dish  with  a  4  to  5  per  cent,  solu- 
tion of  caustic  soda. to  75°  C. ;  by  the  action  of  the  soda  solution  an 
easily  soluble  rosin  soap  is  formed.  The  liquid  is  then  filtered  ofl 
and  the  paper  well  washed.  •  To  the  filtrate  a  sufficient  quan- 
tity of  sulphuric  acid  is  added  to  decompose  the  rosin  soap.  Sul- 
phate of  soda  and  free  rosin  being  formed,  the  latter  separates 
as  a  milky  precipitate,  which  is  filtered  off  through  a  weighed 
filter,  well  washed  and  dried  at  100°  C.  To  determine  the 
weight  of  the  rosin  the  weight  of  the  filter  should  be  deducted 
f roiu  the  total  weight  found.  If  the  milky  -precipitate  at  first 
runs  through  the  pores  of  the  filter,  the  filtrate  is  poured  back 
onto  the  filter  till  the  liquor  runs  clear  through. 

Starch  is  used  in  siting  to  improve  the  appearance  of  paper  and 
to  give  it  a  good  finish.  The  use  .of  starch  alone  for  the  purpose 
of-  sizing  is  far  older  than  the  use  of  rosin  ;  starch  sizing  is  'but  a 
thing  of  the  past.  For  example,  Weisuer  has  found  that  all  the 
papyrus  belonging  to  the  Archduke  Rainer  was  prepared  for 
writing  on  by  means  of  starch  paste.  The  first  known  use  of 
animal  sizing  in  paper  was  in  the  year  1377. 

A  solution  of  iodine  is  used  for  testing  starch  in  papery  if  a 
drop  of  this  solution  is  applied  to  a  paper  containing  starch, 
it  will  cause  a  blue  or  violet  coloration.  The  iodine  solution  must 
be  very  dilute,  or  the  coloration  of  the  paper  will  be  Iiidden  by 
the  brown  color  of  the  solution  itself* 

The  quantitative  determination  of  starch  may  be  carried  out 
according  to  a- suggestion  of  Dr.  Wiirster,  as  follows:  A  strip  of 
the  paper  weighing  from  0.5  to  1.5  gramme  is  boiled  for  a  few 
minutes  in  absolute  alcohol  containing  a  drop  or  two  of  hydro- 
chloric-acid,  when  the  rosin  contained  in  the  paper  will  go  into 
solution-.  The  strip  is  next  washed  in  absolute  alcohol,  dried 
at  100  C.,  and  the  weight  determined.  The  paper  which  has 
been  thus  freed  from  rosin  is  next  boiled  with  50  per  <2ent.  alcohol 
containing  a  few  drops  of  hydrochloric  aoid,  until,  when  moistened 
with  iodine  solution,  it  no  longer  shows  a  light  blue  coloration ; 
it  is  then  washed  in  alcohol,  dried  at  100°  C.,  and  the  weight  deter- 
mined. The  loss  in  weight  is  the  amount  of  starch  present . 


PAPER- TESTING.  435 


The  methods  followed  in  our  own  laboratory,  for  the  detection 
and  estimation  of  starch  in  paper,  differ  from  those  given  above 
and  are  us  follows :  — 

In  making  a  qualitative  test  for  starch  we  do  not  apply  the 
dilute  iodine  solution,  directly  to  the  paper,- as  the  distinctness  of 
the  reaction  is  apt  to  be  impaired  by  the  color  which  the  paper 
itself  takes  on  even  when  starch  is  absent.  Instead  we  tear  the 
paper  into  small  bits  and  boil  these  for  ten  or -fifteen  minutes  ill 
water.  The  solution  is  then  poured  off  and  allowed  to  become 
cold,  when  a  drop  of  dilute  iodine  solution  is  added.  If  starch  is 
present,  there  is  at  once  developed  a  pronounced  blue  coloration. 

The  determination  of  the  amount  of  starch  is  effected  by  con- 
verting the  starch  into  glucose  by  boating  with  dilute  acid,  and 
estimating  the  glucose  by  means  of  the  well-known  method  with 
Fehling's  solution.  The  glucose  found  multiplied  by  0.91  gives 
the  equivalent  starch. 

In  the  conversion  of  starch  into  glucose  careful  regard  must' be 
had  to  the  strength  of  acid  employed,  and  to  the  manner  of  heating, 
since  under  other  circumstances  cellulose  itself  is  converted  into 
glucose.  We  have  found  by  experiment  that  a  solution  containing 
2  per  cent,  by  weight  of  sulphuric  acid  (H2SO4)  does  not  attack 
cellulose  appreciably  when  the  heating  is  conducted  in  the  water 
oven,  while  it  converts  starch  completely  under  the  same  conditions. 
Thcj  best  plan  0f  procedure  is  to  boil  5  grammes  of  the  paper  with 
about  500  cc.  of  water  for  some  time  to  disintegrate  the  fibre  and 
^eilatinize  all  starch.  The  weight  of  the  solution,  which  should  be 
at  least  500  grammes,  is  determined,  and  2  per  cent,  of  sulphuric 
acid  added  to  it.  It  is  then  brought  again  to  boiling  and  transferred 
to  the  water  oven,  where  it  is  kept  until  a  drop  of  the  solution 
mixed  with  a  drop  of  very  dilute  iodine  solution  gives  no  blue 
color.  About  three  hours'  heating  is  generally  sufficient.  Jt  is 
then  allowed  to  cool,  transferred  to  a  litre  flask,  and  potash  or  soda 
added  in  excess.  The  whole  is  made  to  1000  cc.,  and  a  portion 
filtered  for  the  determination  of  glucose  by  Fehling's  solution. 

The  extent  to  which  a  pap^r  has  been  sized  is  usually  determined 
in  the  mills  and  among  buyers  by  pressing  the  tongue  against  the 
sheet  and  then  holding  the  paper  to  the  light.  With  a  .well-sized 
writing  paper  scarcely  any  difference  is  noticed  between  the  por- 
tion thus  moistened  and  the  rest  of  the  paper,  but  other  papers 
appear  more  or  less  transparent  where  they  have  been  wetted 


436  THE  CHEMISTRY  OF  PAPER-MAKING. 

according  to  the  extent  to  which  the  sizing  has  been  carried.  To 
replace  this  very  crude  test,  Leonhardi  has  worked  out  a  method 
which  indicates  with  considerable  definiteness  the  thoroughness 
with  which  the  paper  has  been  sized. 

To  carry  out  Leonhardi's  method,  a  solution  of  ferric  chloride 
of  such  strength  as  to  contain  1.531  per  cent,  of  iron  is  required.. 
This- solution  is  comparable  in  its  power  of  penetrating  the  paper 
to  the  better  grades  of  writing-inks.  An  ivory  ruling-pen  of  the 
form  used  by  draughtsmen,  and  with  rounded  tips  1  mm.  apart, 
is  used  for  drawing  with  the  above  solution  a  number  of  parallel 
lines  upon  the  paper.  The  lines  are  allowed  to  dry,  and  then  a 
weak  solution  of  tannic  acid  in  ether  is  poured  upon  the  other 
side  of  the  paper.  This  ether  evaporates  almost  at  once,  leaving 
the  tannic  acid.  If  the  paper  has  been  badly  sized,  the  ferric 
chloride  solution  will  have  so  penetrated  to  the  under  side  that 
upon  pouring  on  the  tannic  acid  solution  dark  lines  due  to  tannate 
of  iron  appear,  while  with  a  very  well-sized  paper  only  the  yellow 
lines  caused  by  the  ferric  chloride  will  be  noticed  when  the  paper 
is  held  to  the  light. 

An  objection  has  been  made  to  the  etherial  solution  of  tannin, 
because  it  may  dissolve  rosiu  size  to  some  extent,  and  a  solution, in 
water  is  therefore  sometimes  and  perhaps  better  used  instead. 
This  is  applied  to  the  back  of  the  paper  by  a  bit  of  cloth  or  ball  of 
cotton-wool,  and  the  excess  is  taken  up  by  blotting-paper. 

It  is  not  really  necessary  to  use  the  ruling-pen  for  the  ferric 
chloride  solution,  which  may  instead  be  dropped  upon  the  paper 
to  be  tested  from  a  pipette.  To  eliminate  the  error  due  to  the 
thickness  of  the  paper  the  drop  may  be  allowed  to  remain  as  many 
seconds  as  the  paper  per  square  metre  weighs  in  grammes.  This 
of  course  is  purely  arbitrary,  but  when  adhered  to  uniformly  in  all 
tests  permits  of  comparison  between  different  papers.  At  the  end 
of  the  time  the  unabsorbed  solution  is  removed  by  blotting-paper, 
and  when  the  spot  has  dried,  the  tannic  acid  solution  is  applied  to 
the  other  side.  Care  should  be  taken  to  have  the  drops  from  the 
pipette  of  a  size  as  nearly  uniform  as  possible. 

Capillary  Power  of  Blotting-papers.  —  This  may  be  determined 
with  considerable  accuracy,  by  cutting  a  strip  of  the  •  paper  and 
marking  upon  it  with  a  pencil  the  divisions  of  a  millimetre  scale. 
The  paper  is  then  suspended  over  water  and  lowered  until  it  dips 
into  the  water  sufficiently  to  bring  the  zero  point  on  the  scale  at 


PAPER-TESTING.  437 


the  surface  of  the  water.  The  height  in  millimetres  to  which  the 
water  is  drawn  by  the  capillary  action  of  the  paper  is  then  noted 
at  short  intervals  up  to  ten  minutes.  This  may  range  from  about 
100  mm.  in  case  o£  the  best  samples,  down  to  20  mm.  in  case  of 
especially  poor  ones. 

Free  Acids  anil  Chlorides. — If  the  bleach  is  not  thoroughly 
washed  out  of  the  half-stuff  or  neutralized  by  antichlor,  it  does  not 
remain  iu  the  paper  as  hypoehlorite  for  any  length  of  time.  The 
chlorides  formed  by  its  reduction  are,  however,  believed  to  bo 
objectionable,  and  to  hasten  the  deterioration  of  the  paper.  They 
may  be  detected  by  cutting  a  piece  about  six  inches  square  into 
small  bits,  covering  these  with  water  in  a  beaker  and  boiling.  To 
the  cold  solution  slightly  acidified  with  nitric  acid  a  few  drops  of 
silver  nitrate  solution  are  added,  when  chlorides,  if  present,  deter- 
mine the  formation  of  a  white  precipitate  or  opalescence. 

Free  acid  or  an  acid  alum,  if  the  last  is  present  as  such,  weaken) 
the  paper  in  time  through  formation  of  hydrocellulose.  It  is 
difficult  to  determine  free  acid  qualitatively  in  the  presence  o~f 
alum  with  certainty,  since  the  alum  itself  affects  the  indicators 
used,  but  for  practical  purposes  it  is  generally  sufficient  to  boil  up 
the  paper  as  in  the  test  for  chlorides,  and  then  to  add  litmus 
solution  or  congo-recl. 

Determination  of  Ash.  —  This  is  a  matter  of  importance  to 
both  the  maker  and  the  buyer  of  paper,  since  it  enables  the  one 
to  determine  what  per  cent,  of  the  iiiler  used  has  been  retained  in 
the  sheet,  while  it  points  out  to  the  other  the  extent  to  which  the 
paper  'has  been  weighted.  The  test  is  very  easily  carried  out 
although  in  unskilled  hands  it  is  apt  to  give  too  high  results,  owing 
to  imperfect  combustion.  Two  grammes  of  paper  are  taken,  and 
after  being  folded  into  as  small  a  compass  as  possible  are  placed  in 
a  crucible,  and  the  cover  put  on.  A  moderate  heat  is  then  applied 
until  no  more  smoke  or  inflammable  vapor  appears.  The  crucible 
is  then  placed  on  its  side  upon  the  triangle,  and  the  cover  is 
inclined  so  as  to  throw  the  heat  well  into  the  crucible.  The  whole 
is  raised  to  bright  redness,  and  this  temperature  is  maintained  until 
the  ash  is  white,  if  the  paper  were  not  colored,  or  in  any  case 
until  all  carbon  is  burned  off.  The  crucible  and  its  contents  are 
cooled  in  a  desiccator  and  weighed.  From  this  weight  is  taken 
the  weight  of  the  crucible,  and  the  remainder  is  of  course  the 
weight  of  the  ash.  This  divided  by  2  gives  the  per  cent,  of 


498  THE  CHEMISTRY  OF  PAPER-MAKING. 

which  for  most  practical  purposes  may  be  taken  without  cor- 
rection as  representing  the  percentage  of  the  mineral  filler  in  the 
sheet. 

In  very  careful  work,  allowance  may  sometimes  be  made  for  the 
ash  normally  derived  from  the  fibres  composing  the  paper ;  the 
figures  obtained  by  several  chemists  are  given  below :  — 

ASH  IN  COMMERCIAL  PULPS. 
W.  Herzberg. 

Per  cent. 

Sulphite  (1) .     ..-;<   V  V    .  0.48 

Sulphite  (2)     .     .;  .     .     .  >     .    ,*./.:.     .  0.51 

Sulphite,  bleached     .    v    .    ,    .»  -.';." ;...".     .  0.42 

Soda  .     .     .,;,-*     .     .     .    ,   V   .  .  v  '-.:   .   '...     .  1.34 

Soda,  bleached      ...».•'?    -     -  V    .     .  1.40 

Straw.     .;.v    ,,!v    .-   ... /„.  Y   .  ,  .'    .     .     .     .  2.30 

Straw,  bleached  *...'«•  .-•  ."- -sW 1-3^ 

Ground  wood  (pine)      »    .     .    ..     *    .     .     .     .  0.43 

Ground  wood  (fir)    .     ..    f     ;,,..,/..     .  0.70 

Ground  wood  (aspen)   .     .     .     ..    *    .     .     .     .  0.44 

Ground  wood  (lime) :  ,   .  k     .  0.40 

Linen.     .     .     .     .  •  .     .     .     .     .     .     .     .    .  .  .  0.76 

Linen,  bleached 0.94 

Cotton     .    .     .     ...  ' 0.41 

Cotton,  bleached  .     :    .  .-..   .'  .    .....  0.76 

ASH  ix  FIBRES. 
Dr.  Muller. 

Per  rect 

Cotton -    .    ...   ,<->    ,     .     0.12 

Fine  heckled  Flemish  flax      :,„..,,.     .     .     0.70 

Italian  hemp 0.82 

China  grass . 2,87 

Bhea 5.63 

Jute 1.32 

Phormium  tenax 0.63 

Best  Manila  hemp 1.02 

Esparto .      3.50-5.04 

Adansonia 4.72-6.19 

Sulphite  fibre  (Dr.  Frank)     .     ,     .     .     .      0.46-2.60 
Soda  fibre  (Dr.  Frank)      .     .     .     ...      1.00-2.50 


PAPER-TESTING.  439 


,  Various  other  determinations  will  be  found  in  the  chapter  on 
Fibres.  We  have  ourselves  tested  samples  of  cotton  half-stuff  in 
which  the  ash  ranged  from  0;13  to  0.57  per  cent.  Our  figures  i or 
ground  spruce  wood  are  from  0.25-0.32  per  cent.,  while  in  case  of 
sulphite  pulps  the  ash  has  varied  from  0.22  per  cent,  to  over  &00 
per  cent. 

The  difficulty  at  once  met  in  any  attempt  to  correct  the  ash  by 
means  of  the  figures  given  above,  is  that  these  figures  themselves 
are  liable  to  vary  so  much  according  to  the  thoroughness  of  the 
different  treatments  to  which  the  fibres  have  been  subjected  that" 
there  is  danger  of  introducing  a  considerable  error  in  attempting 
to  guard  against  a  slight  one. 

In  order  to  obtain  results  which  fairly  represent  the  average  of, 
mineral  matter  in  the  paper,  several  samples  should  be  tested.  An 
•  uneven  pull  on  the  suction  boxer  may  easily  cause  the  amount  of 
filler  to  vary  by  2  per  cent,  on  the  different  sides  of  the  machine. 
Owing  to  settling  and  other  causes,  an  even  greater  difference  may 
appear  in  the  different  stages  of  a  run. 

Determination  of  the  Kind  of  Filler,  —  This  is  necessary  if 
one  desires  to  know  accurately  the  amount  uf  weight  actually  added 
to  the  paper  or  the  exact  percentage  of  fibre  which  the  paper  carries. . 

A  test  Showing  the  ash  to  contain  large  amounts  of  silica  and 
alumina  is  all  that  is  needed  to  prove  tho  presence  of  clay.  To 
make  this  test,  transfer  the  ash  to  a  porcelain  dish,  add  sufficient 
hydrochloric  acid  to  moisten  thoroughly,  and  then  bring  the  con- 
tents of  the  dish  to  a  temperature  of  120-130°  C.  on  a  sandbath 
until  all  the  acid  is  driven  off.  The  ash  is  then  boiled  up  with 
water  to  which  a  few  drops  of  hydrochloric  acid  are  added,  and 
the  whole  finally  thrown  on  a  filter.  A  white  residue  on  the  filter 
is  silica.  If  ammonia  added  in  very  slight  excess  to  the  hot  fil- 
trate throws  dowii  a  flocculent,  bulky,  White  precipitate,  alumina  is 
present.  The  precipitate  may  be  more  or  less  colored  if  iron  also 
is  present. 

To  some  of  the  above  liquid  cleared  either  by  filtering  or  by 
decantation,  add  ammonium  oxalate  solution.  -If  there  is :a  slight 
cloudiness,  it  is  doubtless  due  to  lime  derived  from  the  clay,  but  a 
considerable  precipitate  indicates  that  the  ash  contains  sulphate 
of  lime,  and  that  the  filler  used  was  either  pearl  hardening, 
fibrous  alumine,  or  gypsum.  Either  of  these  fillers,  if  used  with- 
out clay,  should  give  a  very  white  ash  entirely  soluble-  in  water 


440          '  THE  CHEMISTRY  OF  PAPER-MAKING. 

acidulated  with  hydrochloric  acid:  300-400  c.c.  of  water  in  suc- 
cessive portions  should  be  used  in  all.  Such  ash  rarely"  contains 
grit,  and  often  shows  a  needle-like  crystalline  structure  when 
examined  under  a  hand  glass. 

Agalite  also  gives  a  very  white  ash,  but  this  rubbed  between  the 
teeth  shows  grit.  It  should  give  a  test  for  silica  and  magnesia, 
both  in  large  amounts.  The  test  is  made  by  fusing  the  ash  in  the 
crucible  with  about  five  times  its  weight  of  a  mixture  of  potassium 
and  sodium  carbonates  in  equal  amounts.  The  fused  mass  is 
dissolved  in  water,  and  after  solution  is  complete,  a  few  drops  of 
hydrochloric  acid  are  added.  The  solution  is  then  run  down 
to  dryness  in  a  porcelain  dish,  ignited  at  130°  C.,  until  the  acid 
is  driven  off,  then  boiled  up  with  water  and  filtered. 

A  white  residue  on  the  paper  is  silica.  The  filtrate  is  tested  for 
magnesia,  as  described  under  Magnesia. 

The  ash  from  any*  paper  rarely  contains  a  notable  quantity  of 
alumina  derived  from  alum  used  in  sizing. 

If  the  examination  outlined  above  shows  the  ash  to  consist  of 
sulphate  of  lime,  the  percentage  of  ash  found  should  be  multiplied 
by  1.26  to  find  the  peioentage  of  the  filler  actually  in  the  paper. 
This  is  because  the  sulphate  of  lime,  as  it  exists  in  the  paper,  is 
combined  with  two  molecules  of  water  of  crystallization,  which 
add  proportionately  to  the  weight  of  the  paper,  but  are  driven  off 
upon  ignition  of  the  ash.  Glays  also  often  have  a  definite  per- 
centage of  combined  water,  which,  although  present  in  the  paper 
to  make  weight,  is  similarly  driven  off  on  ignition.  This  percentage 
varies,  however,  in  different  clays,  so  that  no  general  factor  can 
be  given  for  use  in  all  cases.  The  amount  of  this  combined  water 
should  be  determined  in  the  clay  used  and  the  proper  factor  found. 
The  per  cent,  of  ash  multiplied  by  this  factor  gives  the  percentage 
of  weight  actually  due  to  the  clay  in  the  paper.  This  corrected 
percentage  subtracted  from  100  gives  the  per  cent,  of  fibre  in  the 
sheet.  To  figure  retention,  divide  the  pounds  of  fibre  furnished 
by  the  per  cent,  of  fibre  in  the  paper.  The  quotient  is  the  pounds 
of  paper  made  from  the  engine.  From  this  figure  subtract  the 
pounds  of  fibre  furnished,  and  the  balance  is  the  pounds  of  filler 
retained.  This  figure  divided  by  the  pounds  of  filler  furnished 
gives  the  percentage  of  the  filler  retained. 

If  mineral  colors  have  been  used  in  making  the  paper,  some- 
thing toward  their  recognition  may  be  deduced  from  the  character 


PAPER-TESTING.  441 


of  the  ash.  Iron  is  recognized  by  the  brown  color  of  the  ash, 
and  maybe  determined  by  fusing  as  under  Agalite,  and  treating 
the  hot  solution  with  ammonia.  Its  presence  in  considerable 
amount  may  indicate  ochre,  Venetian  red,  Indian  red,  or  Prus- 
sian blue,  the  color  of  the  paper  being  of  course  an  aid  in  reach- 
ing a  conclusion  as  to- which  of  these  colors  is  present.  Chromium, 
if  lead  is  absent,  indicates  chrome  green.  In  the  presence  of 
lead  it  indicates  chrome  yellow,  or  if  the  paper  is  red,  a  basic 
chromate  of  lead.  Lead  alone,  if  the  paper  is  buff,  is  probably 
derived  from  orange  mineral.  Ultramarine  colors  the  ash  blue, 
and  its  amount  may  be  determined  in  many  cases  by  carefully 
igniting  a  considerable  quantity  of  the  paper  until  all  carbon  has 
been  burned  off,  then  taking  a  quantity  of  ignited  clay  or  sulphate 
of  lime  equal  to  the  weight  of  the  ash  and  finding  how  much  of 
a  standard  sample  of  ultramarine  must  be  mixed  with  this  to 
produce  the  depth  of  color  shown  by  the  ash. 

Microscopical  Examination.  —  The  study  of  the  fibres  used  in 
paper-making  can  only  be  conducted  by  the  aid  of  a  good  micro- 
scope, and  a  working  knowledge  of  the  instrument  can  be  put  to 
practical  use  in  many  ways  by  the  paper-maker.  The  value  til 
any  particular  microscope  depends  mainly  upon  the  excellence 
of  the  lenses,  but  the  purchaser  should  also  have  regard  for  the 
steadiness,  ease  of  adjustment,  arid  simplicity  of  construction  of 
the  stand.  For  present  uses  the  preference  should  be  given  to  an 
instrument  having  a  short  tube  and  low  stand.  Magnifying  powers 
ranging  from  70  to  500  diameters  may  be  secured  by  the  combina- 
tions of  two  eyepieces  and  two  objectives,  while  in  general  one 
objective,  giving  with  the  eyepiece  an  enlargement  of  70  diameters, 
will  be  found  sufficient  for  most  examinations.  Low  powers 
which  bring  out  the  details  wanted  are  to  be  preferred  to  higher 
ones. 

The  sample  for  microscopical  examination  is  prepared  by  cutting 
a  few  square  inches  from  different  portions  of  the  sheet  and 
tearing  the  pieces  into  little  bits.  These  are  boiled  for  about 
fifteen  minutes  in  a  1  per  cent,  solution  of  caustic  soda.  The 
whole  is  then  poured  upon  a  sieve  having  a  mesh  which  is  at 
least  as  fine  as  100  to  the  inch,  and  the  paper  which  remains  upon 
the  sieve  is  gently  rubbed  with  the  finger  to  separate  the  fibres. 
To  complete  the  separation,  the  pulpy  mass  is  transferred  to  a 
bottle  with  a  lew  garnets  or  bits  of  glass  and  sufficient  water 


442  THE  CHEMISTRY  OF  PAPER-MAKING. 

to  about  half  .fill  the  bottle*  The  bottle  is  shaken  vigorously 
until  air  lumps  are  broken  up  and  the.  material  brought  to  about 
the  consistency  of  stuff  as  it  flows  onto  the  paper  machine. 

The  jonly  way  by  which  the  student  can  fit  himself  for  the 
microscopical  examination  of  papers  is  by  the  careful  study  and 
comparison  under  the  microscope  of  slides  prepared  from  known 
samples  of  the  different  pulps  arid  fibres  and  standard  admix- 
tures of  them.  .Various  standard  papers  in  which  the  proportions 
of  the  different  fibres  are  stated  are  made  in  Germany  for  use  in 
this  work,  but  it  is  safer  to  make  up  in  the  laboratory  the  different 
mixtures  from  the  pulps  and  to  preserve  them  for  use  at*  needed. 
Following  the  method  given  above  for  preparing  paper  samples 
for  examination,  the  student  should  first  prepare  a  set  of  stan- 
dards from  — 

1.  Pure  linen  paper. 

2.  Pure  cotton  rag  paper. 

3.  Bleached  soda  poplar  fibre. 

4.  Bleached  sulphite  spruce. 

5.  Unbleached  sulphite  spruce. 

6.  Bleached  straw  fibre. 

7.  Bleached  esparto  fibre. 

8.  Half-bleached  jute 

9.  Ground  wood  (spruce). 
10.    Ground  wood  (poplar). 

After  being  properly  pulped,  the  samples  should  be  put  in 
small  "bottles  of  uniform  size  and  shape  and  marked  with  the 
number  of  the  sample  on  a  small  label  oil  the  bottom  of  the 
bottle.  There  should  then  begin  a  thorough  and  systematic 
examination  of  slides  made  from  the  different  samples,  until  the 
characteristics  of  each  pulp  become  familiar.  Attention  should 
be  paid  not  only  to  the  length  and  relative  diameter  of  the  fibres, 
but  to  the  thickenings  and  markings  of  the  cell- wall  and  to 
characteristic  cells,  not  fibres,  which  are  found  in  the  pulp.  A 
frequent  reference  to  Plate  1,  and  to  the  text  in  the  chapter  on 
Fibres  will  be  found  useful. 

Besides  the  physical  features  above  referred  to,  and  upon  which 
the  main  reliance  must  be  placed  for  the  recognition  of  the  dif- 
ferent fibres  certain  distinctive  differences  appear  when  the  fibres 
.are  subjected  to  the  action  of  various  staining  agents.  The  brown 
coloration  noticed  when  a  streak  is  made  with  nitric  aoid  upon 


PAPER-TESTING.  443 


paper  containing  ground  wood  or  other  lignified  fibre  gives  a  rough 
example  of  the  action  of  such  a  staining  agent.  Under  the  micro- 
scope simibr  methods  of  staining  may.be  applied  with  sufficient 
refinement  to  permit  of  a  rough  classification  of  the  different  sorts 
of  fibres  by  means  of  the  colors  which  are  thus  developed.  The 
most  important  of  these  reagents  are  — 

1.  Iodine  Solution.  —  Made  by  dissolving  1  gramme  of  iodine 
and  5  grammes  of  potassium  iodide  in  100  c.c.  of  water.     This 
solution  is  used  alone  or  in  connection  with 

2.  Sulphuric  Acid.  —  The  acid  is  prepared  of  proper  strength 
bj-  mixing  carefully,  in  order  to  avoid  sudden  heating,  three  volumes 
of  sulphuric  acid  of  specific  gravity  1.84  with  one  volume  of  dis- 
tilled water  and  two  volumes  of  pure  glycerine.     It  is  ready  for 
use  when,  it  has  become  cool. 

3.  Aniline  Sulphate,  —  A  saturated  solution  of  the  salt  in  alco- 
hol.    This  stain,«  ground  wood  and  other  lignified  fibres  yellow. 

If,  after  being  thoroughly  beaten  up  'and  separated,  a  small  quan- 
tity of  the  paper  to  be  examined  is  placed  on  the  slide  with  a  drop 
of  iodine  solution,  it  will  be  found  that  the  fibres  may  be  grouped 
as  follows  according  to  the  staining  action  of  the  iodine  upon 
them :  — 

1.  Colorless  Fibres. — -Bleached  chemical  wood  fibre,  bleached 
straw,  and  esparto. 

2.  Fibres  which  are  stained  Yellow* — Ground  wood  and  jute. 

3.  Fibre*- which  are  stained  Brown.  —  Cotton,  linen,  hemp. 
The  use  of  iodine  in  the  identification  of  the  different  fibres  may 

be  further  extended  if  the  iodine  is  employed  in  connection  with 
the  diluted  sulphuric  acid  above  mentioned.  In  this  case  the 
iodine  is  allowed  to  act  for  a  few  minutes  upon  the  fibres  on  the 
slide,  and  the  excess  of  reagent  is  removed  by  carefully  pressing 
down  upon  them  a  small  square  of  blotting-paper.  This  is  raised 
'without  disturbing  the  fibres,  and  after  a  drop  of  the  diluted  acid 
has  been  deposited  upon  them  the  preparation  is  covered  with  a 
thin  cover-glass.  The  staining  effects  thus  developed  are  not  the 
same  as  those  due  to,  the  action  of  the  iodine  alone,  and  are  those 
to  which  occasional  reference  was  made  in  the  chapter  on  Fibres. 

Thus  treated,  fibres  which  consist  of  pure  cellulose, like  cotton,, 
bleached  linen,  straw,  esparto,  and  wood  take  on  a  color  which 
may,  in  case  of  the  different  fibres,  range  from  pure  blue  to  purple 
or  even  to  red  slightly  tinged  with-  blue.  Jute*  ground  wood, 


444  THE  CHEMISTRY  OF  PAPER-MAKING. 

unbleached  and  poorly  cooked  sulphite,  and  other  lignified  fibres 
turn  deep  yellow.  The  staining  also  brings  out  more  clearly  those 
differences  in  structure  which  aid  in  the  recognition  of  the  fibres. 

Aniline  sulphate  solution  stains  the  lignified  fibres  yellow,  and 
is  especially  useful  for  bringing  ground  wood  into  prominence. 

Another  very  delicate  reagent  for  detecting  the  presence  of 
ground  wood  is  phloroglucin.  It  is  employed  in  solution  prepared 
by  dissolving  2  grammes  of  the  reagent  in  25  c.c.  of  alcohol  and 
adding  5  c.c.  of  concentrated  hydrochloric  acid.  It  stains  lig- 
nified fibres  a  brilliant  red. 

When  the  student  has  familiarized  himself  with  the  microscopi- 
cal appearance  of  the  standard  samples,  bottles  should  be  selected 
at  random  from  the  set  and  examined  until  without  reference 
to  the  number  he  finds  himself  able  to  identify  any  sample. 
Standard  mixtures  should  then  be  prepared  by  weighing  off  and 
mixing  the  air-dry  fibres  in  definite  proportions  and  reducing  to 
pulp  as  in  case  of  paper.  The  following  forms  a  convenient  set  of 
such  mixed  standards  with  which  to  begin :  — 

1.  Linen  50  per  cent.,  cotton  50  per  cent. 

2.  Cotton  30  per  cent.,  bleached  popular  fibre  "70  per  cent. 

3.  Bleached  sulphite  spruce  30  per  cent.,  bleached  poplar  70  per 

cent. 

4.  -'Cotton  10  per  cent.,   bleached   sulphite   spruce   20  per  cent., 

bleached  poplar  70  per  cent. 

5.  Unbleached  sulphite  spruce  70  per  cent.,  jute  30  per  cent. 

6.  Unbleached  sulphite  spruce  50  per  cent.,  spruce  ground  wood 

50  per  cent. 

7.  Unbleached  sulphite  spruce  50  per  cent.,  poplar  ground  wood 

50  per  cent. 

8.  Unbleached  sulphite  spruce  20  per -cent.,  spruce  ground  wood  80 

per  cent. 

9.  Unbleached  sulphite  spruce  20  per  cent.,  poplar  ground  wood 

80  per  cent. 

10.  Bleached  poplar  50  per  cent.,  bleached  straw  50  per  cent. 

11,  Bleached  straw  50  per  cent.,  bleached  esparto  50  per  cent. 

Besides  enabling  one  to  determine  the  proportions  in  which 
the  cftfferent  fibres  are  present  in  a  paper,  the  microscope  will 
also  yield  considerable  information  as  to  the  manner  in  which 
these  have  been  beaten.  The  action  of  a  refining  engine  like  the 
Jordan  breaks  or  cuts  many  of  the  fibres,  and  leaves  the  ends 


PAPS&-TSST1JNG.  445     . 


blunt.  Long  beating  in  the  common  beating  engine,  on  the  oj:her 
hand,  breaks  up  the  ends  into  little  tendrils  which  curl  off  in 
every  direction,  and  are  often  quite  separated  from  the  original 
fibre.  If  the  fibres  of  one  sort  are  found  in  this  last  condition, 
while  the  other  fibres  are  nearly  whole  or  broken  sharply  across, 
it  is  safe  to  assume  that  the  much  broken  stock  was  put  into  the 
engine  first  and  given  a  preliminary  beating  before  the  addition 
of  the  rest  of  the  furnish. 

Determination  of  Ground  Wood. — Various  qualitative  methods 
of  extreme  delicacy  have  been  worked  out  for  the  detection  of 
ground  wood  in  paper  which  do  not  require  a  resort  to  the  micro- 
scope. The  well-known  nitric  acid  test,  which  consists  merely  in 
making  a  streak  upon  the  paper  with  concentrated  nitric  acid,  and 
noting  whether  the  brown  color  which  indicates  the  presence  of 
uncooked  wood  is  developed,  is  the  test  most  frequently  employed 
outside  of  Laboratories. 

A  solution  of  aniline  sulphate,  prepared  after  the  manner  already 
described,  is  one  of  the  best  reagents  for  the  detection  of  ground 
wood.  If  the  paper  is  dipped  in  thfc  solution  and  then  allowed  to 
dry,  any  ground  wood  which  may  bo  present  is  stained  yellow,  and 
from  the  depth  of  color  thus  obtained  a  rough  idea  may  be 
formed  of  the  proportion  in  which  ground  wood  enters  into  the 
composition  of  the  sheet. 

Phlproglucin  may  be  used  either  in  the  acid  solution  previously 
mentioned,  or  the  paper  may  first  be  dipped  in  dilute  hydrochloric 
acid,  then  dried  and  wet  with  a  solution  of  phloroglucin  in  alcohol. 
The  pink  or  red  coloration  due  to  liquefied  tissues  is  very  charac- 
teristic, and  the  depth  of  color  may  serve  here,  as  in  case  of  aniline 
sulphate,  to  give  an  approximation  to  the  quantity  of  ground  wood 
in  the  paper. 

It  should  be  noted  in  connection  with  these  tests,  that  what  they 
realty  indicate  is  the  presence  of  lignified  fibre,  and  that  this  is  not 
necessarily  present  in  the  condition  of  ground  wood.  Jute,  for 
instance,  gives  a  brilliant  yellow  with  aniline  sulphate,  and  sulphite 
fibre  which  has  not  been  thoroughly  reduced  responds  similarly  to 
the  reagent.. 

It  has,  moreover,  been  pointed  out  by  F.  v.  Hb'hnel,  that  various 
carbohydrates,  such  as  cane  sugar,  dextrins,  etc.,  give  reactions 
resembling  the  lignin  reactions;  for  instance,  Swedish  filter 
paper,  prepared  from  pure  cellulose,  impregnated  with  cane-sugar 


440  THE  CHEMISTRY  OF  PAPEK-MAKING. 

solution  and  tested  with  phloroglucin  and  hydrochloric  acid  at  first 
gave  no  reaction,  but  when  dry  it  becomes  distinctly  red  just  as 
if  wood  fibre  were  present.  Again,  wood  cellulose^  which  tested  in 
the  ordinary  way  with  phlorogluoin  and  hydrochloric  acid,  showed 
only  traces  of  lignin,  became  intensely  red  when,  after  treatment 
with  the  reagents,  it  was  washed  slightly  and  then  quickly  dried 
at  iOO°~110°  C. 

For  these  reasons  the  only  conclusive  .evidence  of  the  presence 
of  ground  wood  is  that  furnished  by  the  micioscope.  The  fibre 
bun-dies  which  always  occur  in  ground  wood,  and  which  are 
characterized  by  their  broken  ends  and  transverse  markings,  are 
then  easily  recognized.  A  surprisingly  large  proportion  of  the 
fibres  are,  however,  well  separated  and  unbroken,  but  these  with 
the  bundles  stand  out  prominently  when  the  material  on  the  slide 
has  first  been  stained  with  aniline  sulphate. 

A  few  chemical  methods  for  the  quantitative  determination  of 
ground  wood  have  been  proposed,  but  are  rarely  employed,  as  they 
entail  more  work  than  the  matter  usually  warrants,  while  they  are 
not  much  more  accurate  than  a.  careful  microscopical  examination 
which  gives-' ail  approximation  sufficiently  close  for  most  practical 
purposes. 

The  most  satisfactory  of  these  chemical  methods  is  that  of 
Godeffroy  and  Coulon,  which  depends  upon  the  fact  that  lignifiad 
wood  fibre  has  the  property  of  reducing  gold  from  a  solution  of 
gold  chloride  while  the  purer  forms  of  cellulose  which  constitute 
•cotton,  linen,  chemical  wood,  straw,  and  similar  fibres,  do  not  have 
this  power-.  The  present  method  as  simplified  and  othenwiae 
improved  by  Godeffroy  is  as  follows:  — 

Two  equal  portions  of  the  paper  are  taken,  and  both  are  boiled 
for  ten  minutes  in  10  per  cent,  aqueous  ammonia,  then  thoroughly 
washed  and  dried.  One  portion  is  burned,  and  the  ash  determined. 
The  other  portion  is; boiled  for  ten  minutes  with' a  solution  of  gold 
chloride,  then  removed,  washed,  dried,  and  burned.  From  the 
weight  of  ash  obtained,  that  found  in  the  untreated  paper  is 
deducted,  giving  the  weight  of  gold,  which  multiplied  by  100  and 
divided  by  21.2  gives  the  percentage  of  lignoceilulose  in  the  paper. 
The  factor  21.2  represents  the  quantity  of  gold  which  100  parts 
of  eproiund  wood  will  reduce  under  these  conditions  as  determined 
by  mmijerous  experiments. 

Testing  Pulp  for  Moisture. — The  determination  x>l  the  amount 


PAPER-TESTING.  447 


of  moisture  in  a  given  sample  of  pulp  or  paper  is  a  very  simple 
operation,  as  will  appear  from  the  method  given  below.  The  great 
chauce  for  error  lies  in  the  manner  in  which  the  sample  is  drawn, 
and  here  too  much  care  cannot  be>  exercised.  The  following 
methods  of  sampling  are  those  used  in-,  our  own  work,  and  long 
experience  has  shown  us  that  they  give  a  sample  which  fairly  and 
accurately  represents  a  lot  of  pulp. 

If  the  pulp  as  coming  from  the  machine,  a  uniform  strip  2 
inches  wide  should  be  taken  every  twenty  minutes  across  its  entire 
width.  If  the  pulp  is  received  at  the  mill  in  bales,  and  if  these 
can  be  opened  without  too  great  inconvenience,  one  bale  in  ten 
should  be  taken  at  random  from  the  lot  and  opened ;  from  a  sheet 
at  about  the  centre  of  one  of  these  bales  a  strip  1  j-  inches  wide  is 
cut  across  the  width  of  the  sheet.  A  similar  strip  is  cut  from  the 
fifth  sheet  of  the  next  bale.  The  strip  from  the  third  bale  is  cut 
f Tom  tho  centre,  but  this  time  lengthwise  of  the  sheet.  The  sample 
from  the  fourth  bale  is  taken  from  the  fifth,  as  is  the  ease  of  the 
second  bale,  but  lengthwise.  The  whole  number  of  bales  set  aside 
for  sampling  —  that  is,  one  bale  in  every  ten  in.  the  lot—- is  then 
sampled  in  this  order. 

For  sampling  pulp  on  dock,  or  where  for  many  reasons  it  is 
impossible  to  opea  th$  bales>  we  employ  a  special  tool  similar  to 
a  washer  cutter,  but  with  a  heavier  and  longer  blade.  This  tool 
is  used  with  a  bit-stock,  arid  enables  the  sampler  to  easily  cut 
through  25  or  50  sheets,  removing  from  each  a  disk  3  inches  in 
diameter.  The  sampler  first  cuts  through  the  bagging  around  the 
bale  witft  a  knife,  and,  if  the  pulp  is  fairly  thick,  drives  the  tool  in 
until,  on  being  withdrawn,  it  will  remove  25  or  more  disks.  The 
see/ond,  fifth,  tenth,  fifteenth,  twentieth,  and  twenty-fifth  disks  are 
taken,  and  the  others  replaced  in  the  bale.  One  bale  in  every  ten 
is  sampled  in  this  manner,  and,  so  far  as  passible,  in  different  places, 
in  all  cases,  and  this  point  i'&  one  of  tha  first  importance,  the 
moment  the  samples  are  cut 'they  are  at  once  placed  in  a  tin  pail  or 
can  with  tightly  fitting  cover,  which  is  only  removed  to  admit  a 
new  portion  of  tho  sample.  The  can  with  its  con  tents  is  weighed 
in  the  laboratory-.  Then,  and  not  until  then,  is  the  ptdp  removed 
and  the  can  weighed  alone.  The  difference  between  the  two 
weights  gives  the  weight  of  the  sample. 

In  sampling  ground  wood  it  is  sufficient  to  cut  one  bale  in  every 
20.  Tbe  outside  sheet  of  the  first  bale  is  cut,  and  the  centre  of 


448 


THE  CHEMISTRY  OF  PAPER-MAKING. 


the  next  one,  and  so  on.  It  is  sufficient  to  take  a  small  triangular 
piece  instead  of  a  strip,  but  care  should  be  taken  that  the  pieces 
are  about  the  same  siae. 

Some  form  of  water-oven  is  used  for  drying  the  sample ;  that  is, 
a  jacketed  oveu  through  which  a  circulation  of  air  can  be  main- 
tained. The  jacket  is  about  one-third  filled  with  water,  which  is 
kept  at  the  boiling  point  by  a  burner  below  the  oven.  In  this 

way  the  pulp  is  dried  at  a  temperature 
which  never  exceeds  100°  C.  The  ovens 
are  made  with  several  compartments,  so 
that  no  two  samples  are  placed  in  the 
same  compartment.  The  pulp  is  allowed 
to  dry  for  at  least  one  day,  and  is  then 
quickly  transferred  to  a  tin  can,  which 
is  then  covered  at  once,  and  weighed  as 
soon  as  cool.  The  pulp  is  again  trans- 
ferred to  the  oven,  and  the  can  weighed 
in  order  to  determine  by  subtraction  the 
weight  of  the  pulp.  A  second  drying 
for  one  half  day  follows ;  the  pulp  is 
again  weighed  as  before.  If  the  loss  of 
the  weight  does  not  amount  to  more 
than  ^  of  1  per  cent,  on  the  weight  of 
the  original  sample,  the  last  weight  is 
taken  as  the  bone-dry  weight,  and  when 
subtracted  from  the  original  weight  of 
the  sample  gives  the  weight  of  the 
water  which  is  then  calculated  into  per- 
centages. Should  the  difference  between 

O 

the  two  weights  be  greater  than  that 
indicated  above,  the  pulp  must  again 
go  into  the  oven  for  further  drying,  until  two  successive  weights 
agree  within  the  limit  named. 

A  German  drying  oven  which  has  many  points  of  excellence  is 
shown  in  Fig.  93.  The  top  D  may  be  removed  for  the  .introduc- 
tion of  the  sample  into  the  oven  $,  which  is  surrounded  by  a  tvator 
and  steam  jacket,  as  shown.  Around  this  water-jacket  is  a  space 
with  perforations  at  the  top,  open  to  the  atmosphere  and  connected 
at  the  bottom  by  pipes  leading  to  the  oven.  The  air  is  heated 
during  its  passage  down  this  space  and  then  passes  up  through 


.  — DRYING-OVEN. 


PAPER-TESTING. 


449 


the  oven  to  make  its  escape  through  pipe  JT,  its  course  being 
shown  by  the  arrows.  The  thermometer  T  is  not  really  neces- 
sary. The  dotted  lines  within  the  oven  indicate  a  cylindrical 
cage  of  wire  ganze  into  which  the  pulp  may  be  placed.  The 
Knofler  oven,  shown  in  Fig.  94;  is  a 
very  convenient  form*  and  is  so  ar- 
ranged that  the  weight  of  the  pulp  may 
be  read  off  at  any  time.  It  is  quite 
easy  to  determine  when  the  pulp  has 
become  quite  dry  and  to  avoid  over- 
heating. It  consists  of  a  cylinder  with 
a  tightly  fitting  cover,  and  provided  on 
the  outside  -with  a  water  gauge  and  a 
faucet,  as  shown.  Space  for  the  pulp 
in  the  oven  proper  is  formed  by  two 
smaller  cylinders  concentric  with  the 
first ;  the  innermost  or  fbird  cylinder  is 
open  at  the  bottom  and  closed  at  the 
top  so  as  to  form  a  cylindrical  steam 
chamber,  the  bottom  of  which  is  sealed 
by  the  water.  A  small  pipe  connects 
the  top  of  this  space  with  the  upper 
portion  of  the  second  steam  space  out- 
side the  oven  proper.  The  second 
cylinder  projects  down  as  far  as  the 
bottom  of  the  innermost  one,  aftd  the 
two  are  there  joined.  A  section  across 
the  oven  shows  it  therefore  to  be  ring- 
shape,  and  by  this  shape  the  heating 
surface  is  enlarged.  If  pulp* is  to  be 
dried,  it  is  placed  in  the  space  between 
the  two  parts  of  the  wire  gauze  cage 
shown  in  Figs.  95  and  96.  This  is  sus- 
pended from  a  balance  beam  as  shown 
in  Fig.  94.  If  the  material  to  be  dried 

is  a  powder,  the  cage  is  replaced  by  the  series  of  trays  in  Fig.  97. 
Moisture  in  "Air-dry"  Pulp.  — This  is  usually  determined  by 
first  drying  the  pulp  to  constant  weight  at  the  temperature  of 
boiling  water,  and  then  allowing  the  sample  to  remain  exposed  to 
the  air  at  the  ordinary  temperature  for  twenty-four  or  forty-eight 


Fig.  94.  —  KNOFLER  DRYING- 
OVEN. 


450 


THE  CHEMISTRY  OF  PAPER-MAKING. 


hours,  in  order,  that  it  may  take  up  what  is  supposed  to  be  the 
amount  of  moisture  normally  present  in  the  sample  under  ordinary 
atmospheric  conditions.  It  is  hardly  necessary  to  point  out  that 

as  atmospheric  conditions  are  con- 
stantly subject  to  variation  over  wide 
ranges  of  temperature  and  humidity, 
there  is  really  no  such  thing  as  a 
normal  amount  of  moisture  for  any 
given  sample  of  pulp  or  paper.  The 
moisture  in  the  sample  is  at  all  times 
varying  with  the  atmospheric  condi- 
tions, and  these  are  never  precisely 
the  same  in  two  places  at  once.  The 
impossibility  which  thus  arises  of  stat- 
ing with  any  definiteness  what  **  air- 
dry  "  pulp  really  is,  makes  the  air-dry 
basis  a  most  unsatisfactory  one  for 
sales,  and  is  a  source  of  constant  dis- 
Figs.  95-96. -CAGE  FOR  HOLD-  ^  between  buyer  and  seller. 
ING  SAMPLE.  •  / 

Many  attempts  have  been  made  by 

chemists  associated  with  the  paper  trade  in  this  country  and 
abroad  to  put  the  matter  on  a  more  definite,  and  therefore  more 
satisfactory,  basis.  The  experiments  of  Martin  L.  Griffin  are  of 
especial  value,  because  of  their  large  number  and  the 
lengtllof  time  which  they  cover.  These  experiments 
were  carried  on  for  several  years.  During  the  year 
1884,  10  samples  of  soda  poplar  fibre  previously 
dried  at  212°  F.  were  exposed  each  day  in  a  room 
having  windows  open  and  with  no  fire.  The  aver- 
age gain  in  weight  during  the  year  amounted  to  6.38 
per  cent.,  which  represents  the  increase  due  to  the 
absorption  of  the  so-called  atmospheric  moisture. 
During  1886,  from  3  to  5  samples  previously  dried 
as  before,  were  exposed  daily  in  a  well-aired  brick 
storehouse  with  cellar  and  good  floor  and  allowed  fj 
to  remain  there  for  a  week.  The  monthly  average 
which  showed  the  greatest  gain  in  weight  was  in 
November,  when  the  moisture  absorbed  amounted  to  9.39  per  cent. 
The  lowest  was  in  June*  when  the  gain  was  5.40  per  cent.  The 
average  gain  for  the. year  was  7.04  per  cent.  The  method  of  test- 


Pig.  97. 


PAPER-TESTING.  451 


ing  employed  during  the  year  1888  was  somewhat  different,  and 
consisted  in  keeping  20  samples  in  a  sheet-iron  closet  so  arranged 
that  neither  rain  or  snow  could  enter,  although  it  permitted  circu- 
lation of  air.  The  samples  were  weighed  each  day  and  the  fluc- 
tuations in  moisture  noted.  The  samples  were  changed  about 
once  in  three  months.  The  amount  of  moisture  present  ranged 
from  9.21  per  cent,  in  November  and  December  down  to  5.66  per 
cent,  in  the  previous  January.  The  average  for  the  year  was 
7.40  per  cent. 

Gemmell,  in  England,  finds  as  the  result  of  comparatively  few 
experiments,  that  about  10  per  cent.v  of  moisture  is  absorbed.  The 
Norwegian  pulp-makers  claim  as  much  as  12  per  cent. 

Two  ways  of  meeting  the  difficulty  which  arises  from  these 
variations  have  been  proposed.  The  most  logical  one  is,  that  pulp 
should  be  bought  and  sold  upon  the  bone-dry  basis,  with  no 
allowance  for  atmospheric  moisture.  This,  of  course,  means  a 
readjustment  of  prices  to  meet  the  new  conditions  of  sale.  The 
other  and  most  generally  adopted  plan  is  for  the  buyer  and  seller 
to  fix  upon,  by  agreement,  some  arbitrary  percentage  which  shall 
represent  the  air-dry  moisture  in  the  pulp.  As  a  result  of  the 
experiments  of  Dr.  Norton,  8  per  cent,  is  commonly  taken  in  case 
of  ground  wood;  that  is,  92  Ibs.  of  the  bone-dry  pulp  are  said 
to  represent  100  Ibs.  of  the  same  pulp  in  the  air-dry  state. 
Soda  pulp  is  commonly  sold  on  the  basis  of  its  carrying  7.50  per 
cent,  of  atmospheric  moisture,  while  in  case  of  sulphite  fibre  the 
figure  usually  recognized  by  the  trade  is  10  per  cent. 

Where  such  a  basis  has  been  accepted,  the  method  of  figuring 
air- dry  pulp  is  as  follows :  The  sample  is  first  made  bone-dry  by 
drying  in  a  water  oven  to  constant  weight.  The  loss  in  weight 
represents  the  moisture  in  the  sample,  and  is  calculated  into  per 
cents.,;  this  figure,  subtracted  f?om  100,  gives  the  per  cent,  of 
absolutely  dry  fibre.  If  now  the  pulp  were  sold  on  10  per  cent, 
basis,  every  90  parts  by  weight  of  the  bone-dry  pulp  represents  100 
parts  of  air-dry.  If  the  basis  is  8  per  cent.,  92  parts  of  bone-dry 
pulp  are  required  to  make  100  of  air-dry,  while  on  the  basis  of  7.50 
per  cent.,  92.50  parts  of  the  dry  pulp  are  required  to  make  100  of 
the  air-dry.  The  percentage  of  bone-dry  fibre  found  is,  therefore, 
divided  by  90  or  92  or  92.50,  as  the  case  may  be,  and  the  quotient 
multiplied  by  100,  the  product  being  the  percentage  of  air-dry  pulp 
on  tho  basis  taken. 


452  THE  CHEMISTRY  OF  PAPER-MAKING. 


CHAPTER  X. 

ELECTROLYTIC    PROCESSES. 

AT  the  time  electrolytic  processes  for  the  production  of  hypo- 
chlorites  were  first  exploited  in  the  large  commercial  way  it  was 
thought  that  they  offered  to  the  paper-maker  a  direct  and  simple 
method  of  preparing  at  the  mill  the  liquors  required  for  the 
bleaching  of  the  stock,  and  this  on  such  a  basis  of  economy  as  to 
make  it  only  a  question  of  time  when  these  so-called  processes  of 
electric  bleaching  would  supplant  the  older  method,  which  involved 
the  use  of  chloride  of  lime.  With  the  prospect  that  the  paper- 
maker  would  have  added  to  his  other  duties  the  superintendence 
of  such  electrolytic  plants,  it  seemed  desirable  that  a  work  on 
paper-making  chemistry  should  set  forth  in  some  detail  both  the 
chemical  and  electrical  principles  involved  in  their  operation.  At 
the  present  time,  however,  the  state  of  the  art  is  such  as  to  hold 
out  little  probability  that  the  electrolytic  production  of  bleaching 
agents  will  become  a  department  of  the  paper-maker's  work  in  any 
such  general  sense  as  the  recovery  of  soda-ash  or  the  manufacture 
of  bisulphite  solutions  has  already  done.  Any  lengthy  discussion 
of  these  electrolytic  processes  becomes,  therefore,  somewhat  outside 
the  scope  of  the  present  work,  and  it  is,  moreover,  true  that  such 
of  these  processes  as  seem  most  likely  to  have  a  practical  interest 
from  the  paper-maker's  standpoint,  through  their  probable  effect 
upon  the  future  price  of  bleaching-powder,  are  now  so  far  from 
their  final  terms  and  subject  to  such  rapid  development  that  any 
description  of  the  present  forms  of  apparatus  is  likely  within,  a 
short  time  to  havef  only  an  historical  interest.  We  shall  for  these 
reasons  make  no  attempt  to  go  into  the  subject  in  greater  detail  than 
to  present  briefly  the  more  obvious  principles  which  underlie  the 
art,  together  with  the  general  means  involved  in  their  application. 

When  a  current  of  electricity  passes  along  a  metallic  conductor, 
various  magnetic  and  heating  effects  are  observed,  but  the  con- 
ductor itself  does  not  apparently  suffer  change.  Liquids,  like 
other  bodies*, vary  among  themselves  in  their  power  to  conduct 


ELECTROLYTIC    PROCESSES.  453 

electricity;  some,  like  the  oils,  being  among  the  best  insulate*, 
while  others  are  excellent  conductors,  though  never  in  this  respect 
comparable  to  the  metals.  Those  liquids  which  conduct  electricity 
are  termed  "  electrolytes,"  and  it  is  the  peculiarity  of  electrolytes 
that  they  suffer  decomposition  in  direct  proportion  to  the  amount  of 
current  passing  through  them.  The  results  or  products  of  this 
decomposing  action  of  the  current  are  observed  at  those  points 
called  "  poles"  at  which  the  current  enters  and  leaves  the  liquid,  and 
the  operation  itself  is  termed  "electrolysis."  The  point  or  surface 
at  which  the  current  enters  is  called  the  "  anode,"  and  that  at  which 
it  leaves  the  liquid  is  called  the  "  cathode. "  The  liquid  or  that  com- 
ponent of  it  which  is  decomposed  is,  under  the  action  of  the 
current,  split  up  into  two  constituents  called  "ions,"  one  of  which, 
the  "anion,"  is  liberated  at  the  anode  surface,  while  the  other,  the 
"  cathion, "  is  set  free  at  the  cathode  surface.  When,  for  example,  a 
current  is  passed  through  slightly  acidulated  water,  the  products 
of  the  changes  set  up  by  the  current  are  oxygen,  which  appears  at 
the  positive  pole,  or  anode,  and. hydrogen,  which  is  evolved  at  the 
negative  pole,  the  cathode.  The  proportions  of  each  evolved  are 
those  in  which  they  unite  to  form  the  liquid.  If  the  current  is 
sent  through  fused  sodium  chloride,  common  salt,  the  chlorine  is 
evolved  at  the  anode,  and  metallic  sodium  at  the  cathode.  This 
last  is  an  example  of  the  simplest  form  of  electrolysis  in 
which  the  products  obtained  are  those  directly  due  to  the  initial 
decomposition  set  up  by  the  current.  The  electrolysis  of  a  salt 
in  solution  is  complicated  by  various  secondary  reactions  which 
may  or  do  take  place  between  the  liberated  ions  and  the  com- 
ponents of  the  liquid.  If  a  solution  of  common  salt  in  water  is 
electrolysed  while  the  solution  is  at  the  same  timo  mechanically 
agitated,  the  primary  results  of  the  electrolysis  are,  as  in  case  of 
the  fused  salt,  metallic  sodium  and  chlorine,  but  as  a  result  of 
the  secondary  reactions  set  up  by  contact  of  the  liberated  ions 
with  the  liquid  the  final  and  visible  products  are  .hydrogen,  which 
escapes  at  the  cathode,  and  sodium  hypoehlonte,  which  accumu- 
lates in  the  liquid. 

If  the  two  electrodes  are  separated  by  a  porous  partition,  as,  for 
example,  one  of  unglazed  earthenware,  these  secondary  reactions 
do  not  go  so  far,  and  the  final  products  are  hydrogen  and  caustic 
soda  at  the  cathode,  and  gaseous  chlorine  at  the  anode.  Both  the 
caustic  soda  and  the  hydrogen  are,  however,  the  result  of  secondary 


454  Ttiti  CHEMISTRY  OF  PAPKK-MAKINS. 

action  between  the  metallic  sodium  originally  set  free  and  the 
water.  The  quantity  of  an  electrolyte  decomposed  by  the  passage 
through  it  of  a  given  quantity  of  electricity  is  always  the  same, 
but  the  course  of  the  secondary  reactions,  and  therefore  the  nature 
and  quantities  of  the  various  final  products,  may  be  greatly  modi- 
fied by  such  conditions  as  the  temperature  and  concentration  of  the' 
solution,  the  size  and  character  of  the  electrodes,  and  the  strength 
of  current.  For  these  reasons,  when  a  given  product  is  desired, 
there  may  be,  as  the  conditions  of  the  work  vary,  corresponding 
variations  in  the  quantity  of  the  desired  product  obtained.  The 
quantity  found,  divided  by  the  theoretical  amount,  gives  what  is 
called  the  "  current  efficiency  "  of  the  process  or  apparatus. 

In  electro-chemical  work,  as  in  other  departments  of  electricity, 
certain  units  are  employed  for  measuring  and  expressing  the 
strength  and  energy  of  the  current,  the  resistance  of  the  circuit 
around  which  it  flows,  and  the  power  of  the  electromotive  force. 

As  water,  when  in  motion,  possesses  energy,  while  it  would  not 
when  at  rest  and  free  from  strain  be  said  to  have  energy  or  be 
force,  so  electricity,  though  not  to  be  regarded  as  a  form  of  force 
or  energy,  possesses  energy  when  in  motion  and  will  do  work. 
Electricity  in  locomotion,  or  the  electric  current,  presents  many 
analogies  to  flowing  water.  They  are  crude  analogies  and  must 
not  be  pushed  too  far,  but  bearing  this  in  mind  they  may  be  safely 
used  to  obtain  a  clearer  insight  into  the  meaning  and  relations  of 
common  electrical  terms.  When  water  is  pumped  or  carried  from 
the  sea-level  to  a  higher  one,  a  certain  amount  of  work  is  done, 
and  by  virtue  of  its  new  position  the  water  has  an  equal  amount 
of  potential  energy,  which  reappears  when  the  water  is  returning 
to  the  level  from  which  it  came.  A  difference  of  head  is  created, 
and  the  resulting  pressure  causes  the  water  to  flow.  So,  by 
properly  directed  work,  what  may  be  called  a  difference  of  electri- 
cal level  may  be  set  up,  and  this  difference  is  termed  a  "  difference 
of  potential."  Electricity  tends  to  flow  from  a  point  of  high 
potential  to  a  point  of  low  potential,  and  that  which  produces  this 
tendency,  or  which  causes  electricity  to  flow,  is  known  as  "  electro- 
motive force,"  more  briefly  written  E.  M.  F.  The  measure  of 
electromotive  force  is  the  "volt."  The  E.  M.  F.  set  up  by  an  ordi- 
nary DanielFs  cell,  such  as  is  used  in  telegraphing,  is,  roughly 
speaking,  one  volt.  The  measure  of  the  quantity  of  electricity 
which  flows  is  the  "ampere."  The  measure  of  the  resistance  or 


ELECTROLYTIC  PROCESSES.  455 

opposition  to  its  flow  which  the  electric  current  encounters  more 
or  less  in  all  conductors  is  the  "ohm."  It  is  the -resistance  of  a 
column  of  pure  mercury  having  a  cross-section  of  one  square  milli- 
metre and  106  centimetres  long.  One  mile  of  ordinary  telegraph 
wire  has  a  resistance  of  about  ten  ohms.  An  E.  M.  F.  of  one  volt 
will  send  a  current  of  one  ampere  through  a  resistance  of  one  ohm. 
Electricity  always  flows  in  a  closed  circuit,  the  same  quantity 
of  electricity  passing  any  cross-section  of  the  circuit  in  the  same 
time.  The  quantity  of  electricity  which  flows,  measured  in 
amperes,  is  equal  to  the  E.  M.  F.  in  volts  divided  by  the  resistance 
of  the  circuit  in  ohms.  This  statement  of  the  fact  is  known  as 

E 

Ohm's  Law,    and  it   expressed  in  the  formula  C-  — ,  in  which 

H 

(7= the  current  in  amperes,  E—  the  electromotive  force  in  volts, 
and  jR==the  resistance  of  the  circuit  in  ohms. 

Small  currents  moving  under  a  high  electromotive  force,  and 
consequently  through  much  resistance,  are  sometimes  spoken  of 
as  intensity  currents,  while  larger  currents  under  a  low  electro- 
motive force  and  through  low  resistance  are  sometimes  called 
quantity  currents.  A  small  stream  of  water  under  greats  pressure 
will  do  as  much  work  as  a  larger  stream  under  correspondingly 
lower  pressure,  and  so  a  small  quantity  of  electricity  propelled  by 
a  high  electromotive  force  will  do  as  much  work  as  a  much 
greater  quantity  moving  under  a  proportionately  lower  E.  M.  F. 
The  energy  or  power  of  the  current  in  doing  work  is  measured  in 
"watts";  a  current  of  one  ampere  under  an  E.  M.  F.  of  one  volt  has 
an  energy  of  one  watt.  Seven  hundred  and  forty-six  watts  are 
equal  to  one  horse-power.  The  power  of  a  circuit  in  watts  is 
equal"  to  the  product  of  the  number  of  amperes  flowing  multiplied 
by  the  E.  M.  F.  in  volts.  The  most  efficient  dynamos  now  in  use 
generate  a  current  having  a  ^>ower  of  about  680  watts  for  each 
horse-power  at  the  dynamo  pulley. 

The  points  or  terminals  of  a  battery  or  dynamo  to  which  the  ends 
of  the  external  circuit  are  joined  are  termed  poles,  the  point  of 
high  potential,  from  which  electricity  flows  into  the  circuit,  being 
called  the  positive  or  -f  pole,  while  the  point  of  low  potential 
toward  which  electricity  flows  is  known  as  the  negative  or  —  pole. 
A  current  is  said  to  be  continuous  when  it  is  flowing  in  one  direc- 
tion ;  when  the  relation  of  the  poles,  and  consequently  the  direc- 
tion of  flow,  is  subject  to  rapid  reversals,  the  current  is  said  to  be 


456  THE  CHEMISTRY  OF  PAP&&-MAKING. 


an  alternating  one.  The  ordinary  rate  of  reversal  in  commercial 
alternating  currents  is  120  times  per  second.  At  present  the 
continuous  current  is  the  only  one  which  is  adapted  for  electro- 
chemical work. 

The  theory  of  electrolysis  is  roughly  this :  It  is  assumed,  and 
the  assumption  is  justified  by  many  experimental  facts,  that  in  all 
liquids  whicj*  conduct  electricity  there  is  not  only  an  incessant 
movement  of  the  molecules  of  the  liquid,  but  that  probably,  by 
virtue  of  this  motion*  certain  of  the  molecules  are  split  up  into 
their  component  atoms,  and  that  these  free  atoms,  or  ions,  are 
moving  about  in  every  direction  throughout  the  liquid,  combining 
with  other  atoms  as  they  come  within  the  sphere  of  each  other's 
attractive  force,  and  again  splitting  up  and  recombining.  Under 
ordinary  conditions,  when  no  current  is  passing,  the  motion  of  the 
ions  may  be  in  any  direction,  but  under  the  influence  of  the 
current  an  attractive  force  comes  into  play  which  impels  the  ions 
toward  one  electrode  or  the  other,  according  as  they  are  positively 
or  negatively  charged. 

Although  as  a  laboratory  experiment  it  has  been  for  many  years 
an  easy  matter  to  decompose  solutions  of  the  chlorides,  with  pro- 
duction of  hypochlorite  solutions  or  of  free  caustic  and  gaseous 
chlorine,  the  practical  difficulties  in  the  way  of  commercial  opera- 
tion have  been  very  serious.  It  is  necessary  that  the  electrodes 
should  have  large  surfaces  and  be  near  together,  in  order  to  cut 
down  the  resistance  of  the  electrolyte  to  the  lowest  possible  point, 
since  that  portion  of  the  energy  of  the  current  spent  in  overcoming 
this  resistance  is  wasted.  For  the  same  reason,  if  a  diaphragm  is 
used,  it  must  be  of  such  a  nature  as  to  be  efficient  in  preventing 
diffusion  and  yet  of  low  resistance,  and  the  two  qualities  are  in  a 
measure  contradictory.  The  chlorine  and  oxygen  liberated  at  the 
anode  have  a  powerfully  corrosive  action  upon  nearly  all  sub- 
stances, and  yet  the  an^de  must  not  be  appreciably  attacked,  for 
the  double  reason  that  just  so  far  as  it  is  attacked  the  products  of 
the  electrolysis  and  the  anode  itself  are  lost. 

In  spite  of  these  difficulties  there  has  been  within  the  last  few 
years  a  great  advance  in  the  methods  of  commercial  electrolysis, 
and  especially  in  thbse  having  for  their  object  the  decomposition 
of  chlorides.  The  number  of  these  processes  at  the  present  time 
is  large,  and  certain  of  them  have  unquestionably  advanced  beyond 
the  experimental  stage. 


ELECTROLYTIC    PROCESSES.  457 

The  first  electrolytic  process  to  be  seriously  considered  by 
paper-makers  was  that  of  Hermite,  although  Becqueiel,  in  1843, 
noted  that  chlorine  and  soda  are  the  products  of  the  decomposition 
of  salt,  while  Brandt,  in  1848,  claimed  to  have  suggested  as  early 
as  1820  the  application  of  electrolyzed  sea- water  to  bleaching. 
Charles  Watt,  working  with  Hugh  Burgess,  was  probably  the  first 
to  demonstrate  experimentally  the  possibilities  of  the  method,  but 
the  crude  means  then  available  for  generating  the  necessary  cur- 
rent precluded  any  commercial  development.  The  results  of  his 
researches  are  embodied  in  British  patent  No.  13,755,  A.D.  1851. 

Following  Watt  came  numerous  other  experimenters,  until  in 
1886  Hermite  brought  forward  a  well-considered  system  for  the 


FIG.  98.  —  HEKMII  B  ELKCTROLYZER. 

production  of  bypochlorite  of  magnesia,  by  electrolysis  of  a  5  per 
cent,  solution  of  the  chloride. 

Hermite 's  apparatus  consists  of  a  dynamo  capable  of  supplying 
a  current  of  about  1250  amperes,  one  or  more  electrolyzers,  a 
storage  tank  for  liquor,  the  necessary  pumps  and  piping  for  circu- 
lation, and  two  or  more  chests  for  holding  the  pulp  to  be  bleached, 
and  fitted  with  agitators.  The  electrolyzers,  Fig.  98,  consist  of 
galvanized  cast-iron  boxes,  having  at  the  bottom  a  perforated  pipe 
fitted  with  a  cock,  through  which  a  5  per  cent  magnesium  chloride 
solution  is  admitted  from  the  storage  tank  to  the  electrolyzer ;  the 
top  of  each  box  is  surrounded  by  a  channel  in  which  the  solution 
is  received  on  overflowing  the  sides  of  the  box;  from  this  channel 
it  is  carried  away  by  a  pipe,  thus  keeping  up  a  continuous  circu- 
lation. The  negative  electrodes  are  shown  in  the  figure,  and 


458  THE  CHEMISTRY  OF  PAPER-MAKING. 

consist  of  a  number  of  zinc  discs  arranged  upon  two  spindles, 
which  are  caused  to  revolve  slowly  by  means  of  worms  and  wheels. 
Between  each  of  these  discs  is  placed  a  positive  plate,  of  which  a 
view  is  shown  in  Fig.  99.  The  active  surface  of  the  plates  is 

formed  of  platinum  gauze,  mounted  in  a 
frame  of  ebonite  to  give  it  stiffness,  and 
each  plate  is  connected  to  the  copper 
casting  shown  above  the  box  by  means 
of  a  stud  and  nut,  and  can  be  removed 
at  will.  The  positive  terminal  o£  the 
dynamo  is  connected  to  this  copper  cast- 
ing, and  the  current  distributes  itself 
over  the  whole  system  of  platinum  plates, 
which  thus  form  one  large  anode.  It 
passes  from  them  through  the  solution  to 
FIG.  99.— POSITIVE  PLATE.  tne  zinc  discs,  which  form  the  cathode, 

as  they    are   in   contact    with  the   iron 

box  to  which  the  negative  pole  of  the  dynamo  is  connected. 
In  order  to  keep  the  negative  plates  clean  and  free  from  the 
magnesium  hydrate  which  is  deposited  upon  them,  flexible  knives 
are  attached  to  the  ebonite  frames  of  the  positive  plates,  and  these 
knives  scrape  the  surface  of  the  slowly  revolving  zinc  discs. 

Several  electrolyzers,  commonly  ten,  are  generally  joined  up  in 
series,  the  negative  terminal  of  the  first  being  connected  with  the 
positive  terminal  of  the  second,  and  so  on. 

The  solution  of  magnesium  chloride  passing  into  the  electrolyzers 
is  under  the  action  of  the  current  converted  largely  into  one  of 
magnesium  hypochlorite,  the  practical  effect  of  the  reactions  set 
up  by  the  current  being  to  add  an  atom  of  oxygen  to  the  mag- 
nesium chloride  molecule.  The  electrolyzed  solution  then  passes 
directly  upon  the  pulp  contained  in  the  first  of  a  series  of  chests, 
or  engines,  the  pulp  in  the  first  chest  being  that  which  is  most 
nearly  bleached.  The  solution  is  admitted  at  the  bottom  of  the 
chest,  and  passes  upward  through  the  pulp,  and  is  removed  by  a 
washing  cylinder  and  transferred  to  the  second  chest.  The  num- 
ber of  such  chests  in  series  should  be  limited  by  the  rate  of  flow  of 
the  solution,  and  the  rapidity  with  which  the  active  chlorine  is 
exhausted.  Two  or  three  chests  are  usually  sufficient.  A  small 
amount  of  soluble  organic  matter  is  extracted  from  the  pulp  by 
the  solution,  and  as  this  is  of  such  a  nature  that  it  requires  a  little 


ELECTROLYTIC    PROCESSES.  459 

time  for  its  complete  oxidation,  the  liquor  passing  from  the  last 
chest  into  the  storage  tank  should  contain  a  small  residuum  of 
active  chlorine  to  destroy  this  dissolved  organic  matter,  which 
would  otherwise  gradually  accumulate  in  the  solution  and  reduce 
the  efficiency  of  the  process.  Under  conditions  properly  regulated 
in  the  manner  indicated  the  bleaching  action  of  the  solution  is 
extremely  rapid,  and  the  pulp  is  bleached*  to  good  color  without 
loss  of  strength.  This  is  true  t>£  such  refractory  fibres  as  soda 
spruce. 

In  the  process  of  bleaching  the  magnesium  hypochloilte  is  of 
course  reduced  to  the  initial  magnesium  chloride,  and  the  process 
thus  involves  a  complete  cycle  of  changes,  in  which,  theoretically, 
only  the  coloring-matter  of  the  fibre  and  the  pOAver  needed  to  drive 
the  dynamo  are  consumed.  There  is  of  necessity,  in.  practice*  a 
small  loss  of  solution  which  is  carried  away  in  the  bleached 
pulp. 

Each  electrolyzer  working  under  this  system  requires  an  electro- 
motive force  of  five  volts.  Nine  or  ten  electrolyzers  and  an 
expenditure  of  about  eighty  horse-power  are  required  to  produce 
daily  the  equivalent  in  electrolyzed  solution  of  one  ton  of  bleach- 
ing-powder. 

At  the  time  of  its  first  exploitation  the  great  efficiency  of  the 
Her  mite  electrolyzed  solution*  when  used  according  to  his  method, 
led  to  claims  that  its  activity  was  largely  due  to  the  presence  of 
new  and  hitherto  unsuspected  compounds  developed  by  the  elec- 
trolysis. Later  experience  has  shown  these  claims  to  be  unfounded, 
the  superior  efficiency  of  the  solution  being  partly  due  to  the  fact 
that  hypochlorite  of  magnesia  is  in  itself  a  better  bleaching  agent 
than  ordinary  bleaching-powder,  but  still  more  to  the  method  of 
circulation  adopted,  by  which,  as  already  stated,  the  fresh  and 
strong  solution  passed  directly  upon  the  nearly  bleached  pulp  and 
was  finally  exhausted  by  contact  with  the  brown  pulp.  The  solu- 
tion now  used  by  Hermite  is  practically  one  of  common  salt,  only 
a  small  proportion  of  magnesium  chloride  being  added.  His 
process  has  met  with  gratifying  success  in  France,  but  in  this  coun- 
try and  in  England  it  has  encountered  difficulties  which,  though 
not  inherent  in  the  process,  have  proved  a  bar  to  its  introduc- 
tion. 

The  present  tendency  of  development  is  toward  those  processes 
which  have  for  their  object  the  production  of  commercial  bleach 


460  THE  CHEMISTKY  OF  PAPER-MAKING. 


and  alkali,  and  although  certain  to  effect  ultimately  a  material 
reduction  in  the  price  of  these  staples,  they  are  not  likely  to 
introduce  any  radical  changes  into  the  chemical  operations  of  the 
paper-mill.  The  most  prominent  of  these  processes  are  those  of 
Greenwood,  Andreoli,  and  Holland  and  Richardson  in  England, 
and  of  Cutten,  Craney,  Carmichael,  and  especially  Le  Sueur  and 
Waite  in  this  country.  The  fundamental  principles  underlying 
all  these  processes  are  the  same,  the  differences  being  found  in 
the  design  of  the  apparatus  and  in  details  of  work.  All  of  them 
work  with  saturated  brine  and  employ  some  form  of  diaphragm 
between  the  electrodes  to  prevent  diffusion  and  consequent  recom- 
bination of  the  chlorine  and  caustic.  Gas  carbon  has  been  almost 
universally  adopted  as  the  material  for  the  anode,  but  the  design 
and  position  of  the  anode  and  the  means  employed  to  secure 
contact  with  the  conductors  and  to  prevent  too  rapid  disintegration 
of  the  carbon  vary  in  the  different  processes.  Similar  variations 
are  found  in  the  general  arrangement  of  the  decomposing  cell,  the 
electrodes  being  sometimes  placed  horizontally,  while  in  other 
cases,  and  much  more  commonly,  they  stand  in  a  vertical  position. 
The  cathode  is  always  of  iron,  although  mercury  has  been  proposed 
for  certain  forms  of  plant,  and  consists  of  a  plate,  a  casting  of 
special  design,  or  wire  gauze.  In  addition  to  variations  in  the 
material,  form,  and  position  of  the  diaphragm,  the  processes  show 
important  differences  in  the  auxiliary  means  employed  to  further 
limit  the  losses  caused  by  diffusion.  Perhaps  the  best  of  these 
consists  in  maintaining  a  flow  of  the  electrolyte  through  the 
diaphragm,  either  toward  the  cathode  or  to  both  electrodes. 

Although  such  differences  as  have  been  noted  may  appear  as 
minor  ones,  they  are  really  what  determine  the  success  or  failure 
of  a  process,  A  cell  which  requires  six  volts  to  send  a  given 
current  through  it  cannot  compete  commercially  with  one  which 
as  a  result  of  better  design  requires  only  four  and  one-ialf  volts, 
for  this  apparently  slight  difference  means  that  the  former  cell 
requires  the  expenditure  of  38  per  cent,  more  power  than  the 
latter  for  a  given  quantity  of  product. 

It  has  been  already  pointed  out  that  the  present  rapid  develop- 
ment of  these  processes  would  soon  make  obsolete  any  detailed 
account  of  the  several  systems,  but  keeping  in  mind  the  differences 
in  detail  noted  above,  the  following  general  description  may  be 
taken  as  applying  *o  them  all. 


ELECTROLYTIC   PROCESSES.  461 

The  dynamo  for  supplying  the  current  is  so  wound  as  to  deliver 
a  continuous  current  of  large  volume  under  moderate  voltage. 
One  supplying  1250  amperes  at  120  volts  may  be  used  to  advan- 
tage, and  requires  About  225  horse-power.  Large  copper  conductors* 
carry  the  current  to  the  decomposing  cells,  which  are  commonly 
arranged  in  multiple  arc.  That  is,  the  cells  are  arranged  in  sets, 
the  whole  current  going  through  each  set  and  on  to  the  next  set, 
but  only  a  fraction  of  the  current  going  through  a  single  cell. 
This  fraction  varies  from  60  to  500  amperes,  according  to  the  size 
and  construction  of  the  cell,  and  the  number  of  cells  in  a  set  varies 
accordingly.  Each  cell  requires  an  electromotive  force  of  from 
four  and  a  half  to  six  volts.  The  cella  themselves  consist  of 
troughs,  or  vessels,  which  may  be  of  iron  or  slate  or  earthenware, 
but  such  portions  of  them  as  come  in  contact  with  the  chlorine 
must  of  course  be  of  a  material  not  corroded  by  the  element,  and 
this  most  commonly  is  slate  or  earthenware.  Several  cells,  or  at 
least  several  anode  compartments,  may  open  into  a  common  trough, 
or  each  cell  may  be  self-contained.  They  differ  among  themselves 
very  much  in  size,  appearance,  and  construction,  but  each  embodies 
three  essential  elements, —  an  anode  of  gas  carbon,  a  diaphragm  or 
its  equivalent,  and  an  iron  cathode.  The  whole  cell  is  filled  to 
such  a  point  with  saturated  brine  that  both  anode  and  cathode, 
with  of  course  the  diaphragm  between  them,  are  immersed  in 
the  liquid. 

The  current  enters  the  cell  through  the  conductor  connected 
with  the  anode,  and  from  the  anode  passes  through  the  brine  and 
the  saturated  diaphragm  to  the  cathode,  where  it  makes  its  exit  by 
another  conductor.  The  chlorine  evolved  at  the  anode  leaves  the 
liquid,'  and  being  confined  by  the  walls  of  the  anode  compartment 
passes  off  into  pipes  leading  to  absorption  chambers  containing 
lime,  or,  if  a  solution  is  wanted  for  use  at  once,  into  agitating 
apparatus  containing  milk  of  lime.  The  hydrogen  liberated  at 
the  cathode  either  passes  off  directly  into  the  air,  or  the  construc- 
tion of  the  apparatus  may  be  such  that  it  is  confined  until  it  makes 
its  way  out  through  pipes.  The  caustic  soda  fornied  oa  the 
cathode  by  reaction  of  the  water  with  the  metallic  sodium  set  free 
by  the  current  gradually  accumulates  in  the  liquid,  and  either 
flows  off  automatically  as  a  strong  solution  or  ia  drawn  off  from 
time  to  time,  either  for  use  directly  or  for  concentration  by  heat 
in  order  to  separate  the  accompanying  salt  by  crystallization  and 


462  THE  CHEMISTRT  OF  PAPER-MAKING. 

to  secure  the  solid  hydrate.  Such  plants  have  shown  in  practice 
an  efficiency  ranging,  according  to  their  type,  from  5€  to  90  per 
cent,  of  the  theoretical,  or,  ia  other  words,  have  produced  from 
18.12  grammes  to  32.62  grammes  of  caustic,  and  from  16.08 
grammes  to  28.94  grammes  of  chlorine  per  ampere  day,  the  the- 
oretical yields  being  36*24  grammes  of  caustic  and  32.16  grammes 
of  chlorine. 


APPENDIX. 


APPENDIX, 


RULES    FOR    THE    SPELLING    AND    PRONUNCIATION    OF 
CHEMICAL    TERMS. 

Adopted  by  the  American  Association  for  the  Advancement  of  Science  in  1891. 

GENERAL    PRINCIPLES   OP   PRONUNCIATION. 

1.  The  pronunciation  is  as  much  in  accord  with  the  analogy  of  the  English 
language  as  possible. 

2.  Derivatives  retain  as  far  as  possible  the  accent  and  pronunciation  of  the 
root  word.     N 

3.  Distinctly  chemical  compound  words  retain  the  accent  and  pronunciation 
of  each  portion. 

4.  Similarly  sounding  endings  for  dissimilar  compounds  are  avoided  (hence 
-Sd,  -Ite). 

ACCENT. 

In  polysyllabic  chemical  words  the  accent  is  generally  on  the  antepenult ;  in 
words  where  the  vowel  of  the  penult  is  followed  by  two  consonants,  an,d  in  all 
words  ending  in  -ic,  the  accent  is  on  the  penult, 

PREFIXES. 

All  prefixes  in  strictly  chemical  words  are  regarded  as  parts  of  compound 
words,  and  retain  their  own  pronunciation  unchanged  (as  a'ceto-,  d'mido-,  d'zo-, 
hy'dro-,  I'so-,  nl'tro,  nHro'.so-) . 

ELEMENTS. 

Iii  words  ending  in  -ium,  the  vowel  of  the  antepenult  is  short  if  i  (as 
Iri'diwri),  or  y  (as  didy'mium),  or  if  before  two  consonants  (as  ca'lcium),  but 
long  otherwise  (as  tita'nium,  sete'nium,  chru'mium). 

alu'minum  cd'dmium  co'balt  germa'nium  iron 

a'ntimony  cd'lcium  colu'mbium  glu'cinum  Id'nthanum 

a'rsenic  ca'rbon  co'pper  gold  lead 

bd'rium  ce'rium  dldy'mium  hy'drogen  li'thium 

bi'smuth^biz)  ccesium  e'rbium  Vndium  magne'sium  (zhium) 

bO'ron  cklo'rin  flu'orin  I'odm  ma'nganese  (eze) 

brd'mln  chro'mium  ga'llium  Irfdium  mefrcury 

465 


466  THE  CHEMISTRY  OF  PAPER-MAKING. 


pottfitsiuni 
rhv'dium 

sl'licon 
silcer 

te'rbium 
th&'Uium 

vdnci'dium 

rvbVdium 
ruthenium 
samufrium 

so'dium 
strontium  (jshiuni) 
su'lfur 

ttid'riuin 
tin 
titd'nium 

tftlrium 

zinc 
zirco'nium 

mBtpbdenwn         plfi'tinum  sSle'nium  teltu'rium  Ura'nium 

ni'ckel 

nl'trogen 

fflsmium 

S'xygen 

palla'dium 

phfo'phoms  sc&'ndivm  tti'ntalnm  til'ngsten 

Also :  tfrnarifritum,  phosph&nium,  ku'loyen,  cyd'nogent  &mVdogen. 

Note  in  the  above  list  the  spelling  of  the  halogens,  cesium  and  sulfur;  f  is  used 
in  the  place  of  ph  in  all  derivatives  of  sulfur  (as  wl/urict  tul/Ue,  suffo-,  etc.). 

TERMINATIONS   IN   -1C. 

The  vowel  of  the  penult  in  polysyllables  is  short  (as  cy&'-nic,  ftim&'ric,  ars&nic, 
s/A'cec,  i&dic,  taf|'rtc),  except  (1)  u  when  not  used  before  two  consonants  (as 
merfu'riCf  pr&'sisic),  and  (2)  when  the  penult  ends  iu  a  vowel  (as  benzo'ic,  ole'ic) ; 
in  dissyllables  it  is  long  except  before  two  consonants  (as  ftd'rtc,  cZ'/rtc).  Excep- 
tion :  acS'tic  or  acfftic* 

The  termination  -to  is  used  for  metals  only  where  necessary  to  contrast  with 
-OU3  (thus  avoid  aluminic,  nmmonic,  etc.). 

TERMINATIONS   IN   -CUE. 

The  accent  follows  the  general  rule  (as  pUftinou9t  sft'lfurous,  ph&sphotvus, 
coba'ltous).  Exception:  ac&tous. 

TERMINATIONS   IN  -ate   AND  -ite. 

The  accent  follows  the  general  rule  (as  ft'cetfife,  v&'nad&e);  in  the  following 
words  the  accent  is  thrown  back,  S'bictQtet  a'lcoholale,  d'ceionate,  d'ntimonite. 

TERMINATIONS  IN  -id   (FORMERLY  -ide). 

The  final  e  is  dropped  in  every  «ase  and  the  syllable  pronounced  Id  (as 
ch&rtd,  lf«ftrf,  hy'drtd,  ffxtd,  h&droxld,  xfi'//lrf,  tf'mW,  SfniW,  mtrPxXd). 

TERMINATIONS  IN  -ane,  -ene,  -ine,  AND  -one. 
The  vowel  of  these  syllables  is  invariably  long  (as  mfftMne,  fftkdne,  na'ph- 


,  a'nthraeSne,  prd'plne,  qvl'none,  a'cetone,  ke'tonej. 
A  few  dissyllables  have  no  distinct  accent  (as  benzene,  xylene,  cltene). 
The  termination  -Ine  is  used  only  in  the  case  of  doubly  unsaturated  hydro- 
carbons, according  to  Hoffmann's  grouping  (as  proplne). 

TERMINATIONS   IN   -in. 

In  names  of  chemical  elements  and  compounds  of  this  class,  which  includes 
all  those  formerly  ending  in  -ine  (except  doubly  unsaturated  hydrocarbons)  the 
final  e  is  dropped,  and  the  syllable  pronounced  -In  (as  chlo'rtn,  bro'mtn,  etc., 
a!mlu,  d'niiih,  wo'rpAm,  quanta  (kwl'rttri),  vanMKn,  alloxa'nttn,  absi'nthlnt 
ca'ffcin  co'calfn). 


467 


TERMINATIONS   IN  -ol. 


1'lris  termination,  in  the  case  of  '  specific  chemical  compounds,  is  used  exclu- 
sively for  alcohols,  and  when  so  used  is  neyer  followed  by  a  final  c  The  last- 
syllable  is  pronounced  -61  (as  gly'coi,  'phe'nol,  cr&sdl,  thy'mol  (ti),  ffljj'cerfl,  qul'nol. 
Exceptions  :  alcohol.  a'rgol. 


TERMINATIONS   IN 

This  termination  is  always  pronounced  -Sle,  and  its  use  is  limited  to  com- 
pounds which  are  not  alcohols  (as  Puddle). 

TERMINATIONS   IN   -yl. 

No  fin  ale  is  used;  the  syllable  is  pronounced  -jtt  (as  a'cetgi,  &fm$l,  ce'rotyl, 
<*'$/,  e'thtjl). 

TERMINATIONS   IN   -yde. 

The  y  is  long  (as  8'ldehj/de). 

TERMINATIONS  IN  -meter. 

The  accent  follows  the  general  rule  (as  hydrtf  meter,  baro1  meter,  lactometer). 
Exception  :  words  of  this  tlass  used  in  the  metric  system  are  regarded  as  com- 
pound word?,  and  each  portion  retains  its  own  accent  (as  c?ntime"ter,  mi'lli- 


MISCELLANEOUS  WORDS  WHICH  DO  NOT  FALL   UNDER   THE   PRECEDING   RULES. 

Note  the  spelling:  albumen,  albuminous,  ftlbitminiferous,  asbestos,  gramme, 
radical. 

Note  the  pronunciation:  a'lkalme,  a'lloy  (n.  and  v.),  a'llotropy,  a'llotropism, 
I'somerism,  pd'lymerlsm^  apparatus  (sing,  and  plu.),  aqua  regia,  baiy'la,  centigrade, 
co'ncentrated,  crystallln  or  crystalline,  electro'  lysis,  liter,  mfflecule,  molecular,  no'men* 
da"ture,  de'Jiant,  vdlence,  u'niva"lent,  bl'ca"lent,  trl'ca"lentt  qua'drim"lenb  Wwi*. 


A     LIST    OF    WORDS    WHOSE    USE     SHOULD     BE     AVOIDED     IN    JPAVOfi     OF    THE 
ACCOMPANYING    SYNONYMS. 

For  —  Use  — 

sodic,  calcic,  zincic,  nickelic,  etc.      .     ,  sodium,  calcium,  zinc,  nickel,  etc.,  chlorid, 
chlertd,  etc.  etc.  (vid.  terminations  in  -ic,  supra). 

arstnttted.  hydrogen    .     ......  arsin 

antimojuetied  hydrogen     ......  stibin 

phosphoretted  hydrogen  ......  phosphin 

sulfuretied  hydrogen,  etc.     f     .     .     .     .  hydrogen  sulfid,  etc. 

For—  Use—  For—  Use  — 

faryHium  ...     .     .     glucinum  furfurol    ....    furfurdldehyde 

niobium     .....     coiumbiwn  fucusol      .    .     .     .    fucusaldehyde 

glycerin     .     .     .     .     .     glyctrol  anfeol  .....     methyl  phenaie 


468  THE  CHEMISTRY  OF  PAPER-MAKING. 

For—  Use—  For—  Use  — 

hydroquinone  (and  hy-  phenetol    ....  ethyl  phenate 

drochinon)      .     .     .  qu'tncl  anethol      .     .     .     .  methyl  allylphenol 

pyrocatechin  ....  catechol  alkylogens      .     .     .  alkyl  haloids 

resorcin,  etc resorcinol,  etc.  titer  (n.)  ....  strength  or  standard 

mannite mannitol  titer  (v.)  ....  titrate 

dulcite,  etc dulcitol,  etc.  monovalent    .     .     .  univalent 

benzol benzene  divalent,  etc.      .     .  bivalent,  etc. 

toluol,  etc.      ...     .  toluene,  etc.  quanlivalence     .     .  valence 

thein caffein 

Fate,  fat,  far,  mete,  met,  piue,  pin,  marine,  note,  not,  move,  tube,  tub,  rule, 
my,  y  =  i. 

'  Primary  accent;  "  secondary  accent.  N.B.--The  accent  follows  the 
vowel  of  the  syllable  upon  which  the  stress  falls,  but  does  not  indicate  the  divis- 
ion of  the  word  into  syllables. 


CELLULOSE   DERIVATIVES. 

The  chemistry  of  cellulose  has  recently  been  enriched  by  the  dis- 
covery by  Cross,  Bevan,  and  Beadle  of  the  remarkable  reaction  which 
ensues  when  cellulose  (as  for  example,  in  the  form  of  bleached  poplar 
fibre)  is  exposed  to  the  action  of  caustic  alkali  and  carbon  bisulphide. 
Many  important  industrial  applications  of  the  discovery  have  already 
been  proposed  as  the  new  compound  is  plastic  and  soluble  in  water, 
and  yields  by  its  decomposition  the  original  or  slightly  modified  cellu- 
lose which  may  be  thus  brought  into  the  form  of  films,  sheets  or  masses 
without  fibrous  structure.  We  quote  below  from  the  original  paper 
(Jour.  Chein.  Soc.,  London,  1893,  p.  837). 

Cellulose  Thiosulphocarbonic  Acid;  —  When  cellulose  in  any  of 
its  forms  is  treated  with  a  concentrated  solution  of  sodium  hydrate 
(12.5  per  cent.  Na20),  and  the  alkali  cellulose  thus  obtained  is  exposed 
to  the  action  of  carbon  bisulphide  vapor,  action  ensues,  and  in  the 
course  of  an  hour  or  two  a  yellowish  mass  is  obtained,  which  swells  up 
enormously,  on  treatment  with  water,  and  finally  Dissolves  completely. 
This  soluble  compound  is  a  cellulose  thiocarbonate. 

The  action  proceeds  rapidly  when  the  agents  are  brought  together  in 
the  ratio  — 

2CS2;  30to40H2O. 


The  most  convenient  conditions  for  laboratory  experiment  are  with  the 
alkali  in  the  form  of  a  15  per  cent,  aqueous  solution  of  the  hydrate 
(11  to  12  per  cent.  Na20),  the  proportion  by  weight  of  this  solution 
being  from  3.5  to  4  times  that  of  the  cellulose. 


APPENDIX.  469 


The  crude  solution  obtained  by  dissolving  the  product  in  water,  and 
containing  yellow  by-products  (trithiocarbonate),  yields  the  cellulose 
derivative  in  a  pure  state,  on  treating  it  with  saturated  brine  or  with 
strong  alcohol.  It  is  precipitated  by  the  former  in  a  flocculent  con- 
dition, by  the  latter  in  leathery  masses,  which  may  then  be  further 
washed  with  a  13  per  cent,  solution  of  sodium  chloride  or  65  per  cent, 
alcohol,  respectively.  On  redissolving  in  water  an  almost  colorless 
solution  of  extraordinary  viscosity  is  obtained,  which  exhibits  the 
following  properties :  — 

(a)  /Spontaneous  Coagulation. — After  standing  for  a  period,  depend- 
ing on  the  method  of  preparation  and  purification  adopted,  the  solution 
"  sets  "  to  a  firm  coagulum  of  a  hydrated  cellulose  of  the  same  volume 
as  the  original  solution ;  the  coagulum  then  shrinks  gradually,  becom- 
ing surrounded  with   a  yellow   alkaline   solution   (trithiocarbonate). 
During  shrinkage,  the  cellulose   retains  the  form  of  the  containing 
vessel. 

(b)  Coagulation  determined  by  Heat.  —  The  solution  may  be  evapo- 
rated to  dryness  in  thin  layers  at  temperatures  not  exceeding  50°, 
without  sensible   decomposition,   the   dry  substance   obtained  being 
perfectly  soluble. 

At  70  to  80°,  however,  the  solution  thickens  rapidly,  and  at  80  to 
90°  the  coagulation  is  almost  instantaneous.  These  phenomena  are 
due  to  the  fact  that  the  compound  behaves  as  a  product  of  association 
of  cellulose,  alkali,  and  carbon  bisulphide,  the  coagulation  above 
described  being  a  dissociation  of  the  compound  into  its  constituents. 

(c)  Coagulation  determined  by  Reagents. — From  the   foregoing  it 
will  be  evident  that  the  regeneration  of  cellulose  will  be  determined 
by  reagents,  reacting  either  with  the  alkali  or  the  sulphur  group ; 
thus  acids  and  acid  salts;  sulphites,  and  metallic  oxides  all  increase  the 
rapidity  of  decomposition. 

Characteristics  of  the  Regenerated  Cellulose.  —  We  have 
assumed  that  the  cellulose  is  obtained,  in  the  main,  unchanged  from 
the  solution  as  above  described,  and  this  is  generally  true.  It  shows  a 
general  agreement  with  the  normal  cellulose  in  regard  to  resistanc^  to 
hydrolysis  and  oxidation,  and  it  follows,  from  what  has  been  said,  that 
it  is  similar  in  its  capacities  for  hydration,  and  also  generally  in  its 
physical  properties. 

From  the  above  it  'appears  that  carbon  percentage  is  somewhat 
reduced,  and  it  is  to  be  noted  also  that  the  attraction  of  the  product 
for  moisture  is  increased,  the  normal  hygroscopic  moisture  of  the 
recovered  cellulose  amounting  to  10  per  cent,  as  compared  with  7  per 
cent,  in  the  original  cellulose.  The  original  molecule,  therefore, 


470  THE  CHEMISTRY  OF  PAPER-MAKING. 


appears  to  have  undergone  hydration  in  the  ratio  2  C^VL^O^HzO,  and 
we  find  that,  like  many  other  hydrates  of  the  normal  cellulose,  it  gives 
a  blue  coloration  with  iodine. 

We  have  also  observed  constitutional  features  differing  from  those 
of  the  normal  type,  as  indicated  by  exceptional  behavior  in  interactions 
such  as  those  which  determine  solution  and  the  production  of  the. 
ethereal  derivatives. 

The  constitution  of  the  derivative  may  be  expressed  by  the  general 

•OX 

formula  GS  <  ~  -  ,  X  representing  the  variable  cellulose  unit;  that  is, 

the  acting  residue.  This  is,  however,  not  a  cellulose  residue  pure  and 
simple,  but  an  alkali-cellulose,  a  fact  which  is  to  be  expected  a  priori  » 
and  is  proved  by  treating  the  solution  with  benzoyl  chloride,  when 
cellulose  is  eliminated  as  a  cellulose  benzoate. 

The  formula,  therefore,  may  be  written  CS  <      r  ,  which  will 


be  seen  to  be  in  harmony  with  the  analytical  data  given  above. 

The  compound  may  therefore  be  described  as  the  sodium  salt  of 
alkali-cellulosexanthic  acid. 

The  solutions  of  the  compound  give  bright  yellow  precipitates  with 
mercury  and  zinc  salts,  and  a  more  orange  yellow  with  lead  salts, 
Moreover,  as  stated  above,  the  purified  compound  in  presence  of  a 
certain  quantity  of  water  changes  spontaneously  into  cellulose,  alkali, 
and  carbon-bisulphide,  which  confirms  this  view  of  its  constitution. 
Further,  the  solutions  are  precipitated  by  iodine,  the  precipitate 
being  a  thio-derivative  which  can  readily  be  redissolved  with  formation 
of  the  original  compound.  This  action  carried  out  quantitatively 
gives  fairly  constant  numbers. 


APPENDIX.  471 


LIST   OF   UNITED    STATES   PATENTS    RELATING   TO   THE 
SULPHITE   PROCESS. 

Any  of  the  patents  in  the  following  list  may  be  obtained  from  the 
Patent  Office,  at  Washington,  on  payment  of  10  cents.     Coupon  books 
containing  orders  for  50  patents  are  issued  by  the  office  on  pavment 
of  $5.00. 
Akin,  N.  P.     127008.    May  21,  1872. 

Manufacture  of  sulphurous  acid. 
Albrecht,  J.    See  Bernard,  P.  U 
Archbold,  George.    274250.     March  20,  1383. 

Manufacture  of  paper  pulp. 
Archbold,  George.    Reissue,  10328.    May  22, 1883. 

Manufacture  of  paper  pulp.* 
Ball,  Charles  E.    33607&    Feb.  16,  1886. 

Digester, 
feiron,  Jean  B.     67941.    Aug.  20,  1867. 

Disintegrating  wood  to  form  paper  pulp.    Claims  use  of  alkaline  sul- 
phides and  sulphides  of  lime.    Has  been  cited  as  anticipating  Tilgh- 
man,  but  does  not  properly  bear  upon  the  sulphite  process. 
Bremaker,  Charles.    373810.     Nov.  29, 1887. 

Digester. 
Bremaker,  Charles.    35373.    Dec.  7,  1886. 

Digester. 
Bremaker,  Charles,  and  Michael  Zier,  Sr.    333105.    Dec.  29,  I6o5. 

Digester. 
Brungger,  H.    483828.    Oct.  4,  1892. 

Digester. 
Brungger,  H.    483827.    -Oct.  4,  1892. 

Digester  lining. 
Brungger,  H.    483826.    Oct.  4, 1892. 

Digester  lining. 
Burgess,  T.  P.    432692.    July  15, 1890. 

Apparatus  for  producing  bisulphites. 
Carlisle,  Frederick.    395691.    Jan.  3,  1889. 

Apparatus  for  absorbing  gases. 
Carlisle,  Frederick.    284817.    Sept.  11,  1883. 

Manufacturing  of  hydrated  sulphurous  acid . 
Catlin,  Charles  A.    366153.    July  5,  1887. 

.Sulphite  solution  for  wood  pulp. 
Catlin,  Charles  A.    407818.    July  30,  1889. 

Process  of  charging  liquids  with  gas. 
Claraer,  Francis  J.    283077.    Aug.  14,  1883. 

Treating  lead  to  impart  to  it  the  property  of  adhering  to  other  metals. 
Clapp,  Eugene  H.    305740.     Sept,  30,  1884. 

Digester  and  valve.    Especially  applicable  to  soda  process,  but  valve  is 
of  interest. 


472  THE  CHEMISTRY  OF  PAPER-MAKING. 

Gloss,  Gotthold.     See  Schnurmann. 
Comstock,  W.  O.     453076.     May  26,  1891. 

Digester  lining. 
Corn  well,  C.     432604.     .July  15,  1890. 

Apparatus  for  producing  bisulphites. 
Crocker,  William  O.  and  William  P.     339974.     April  13,  1886. 

Producing  sulphite  or  bisulphite  of  soda. 
Crocker,  William  O.  and  William  P.     406886.    July  16,  1889. 

Digester. 
Crocker,  William  O.  and  William  P.     339975.     April  13,  1886. 

.Process  of  making  bisulphites. 
Curtis,  C.,  and  N.  M.  Jones.     485808.    Nov.  8,  1892. 

Digester. 
Curtis,  C.,  and  N.  M.  Jones.    485809.    Nov.  8,  1892. 

Digester. 
Curtis,  C.,  and  N.  M.  Jones.     485810.     Nov.  8,  1892. 

Digester. 
Curtis,  C.,  and  N.  M.  Jones.    484999.    Oct.  25,  1892. 

Digester. 
Curtis,  C.,  and  N.  M.  Jones.    485000.    Oct.  25,  1892. 

Digester. 
Denton,  A.  A.     339387.     April  6,  1886. 

Apparatus  for  exposing  large  surfaces  of  liquid  to  air,  or  vapor,  or  gas. 
Drewsen,  V.    492196.    Feb.  21,  1893. 

Recovery  of  gas. 
Eaton,  A.  K.     119224.     Sept.  26,  1871. 

Use  of  sulphite  of  sodium  as  a  solvent  in  reducing  wood  to  fibre. 
Ekman,  Carl  D.    253357.    Feb.  7,  1882. 

Treating  wood. 
Ekman,  Carl  D.     Reissue,  10131.    June  6,  1882. 

Method  of  treating  wood. 
Ekman,  Carl  D.     260749.    July  11,  1882. 

Treating  fibrous  vegetable  substances  to  obtain  fibre  suitable  for  paper- 
making. 
Ekman,  Carl  D.     307754.    Nov.  11,  1884. 

Extraction  of  gelatine,  fat,  .and  similar  substances.     Patent  covers  the 

use  of  sulphite  solution,  as  above. 
Ekman,  Carl  D.,  with  George  Fry  and  W.  B.  Espaut.    286817.     Oct.  9,  1883, 

Extraction  of  saccharine  matter  from  vegetable  substances.     Boils  the 

cane,  sugar  beet,  etc.,  Mrith  sulphite  solution. 
Ekman,  Carl  D.     282971.     Aug.  14,  1883. 

Obtaining  coloring-matters. 
Erwin,  Franklin  B.     353056.     Nov  23,  1886. 

Apparatus .     (Digester. ) 
Fisher,  Robert  A.     145496.     Dec.  16,  1873. 

Preventing  corrosion  of  iron  and  steel. 
Flodqvist,  Carl  W.     348457.     Aug.  31,  1886. 

Digester. 


APPENDIX.  473 


Ford,  H.  B.     363457.     May  24,  1887. 

Apparatus  and  process  for  manufacture  of  sulphurous  acid. 
Frambach,  Henry  A.,  arid  Andrew  J.  Volbrath.     348159.     Aug.  24,  1886. 

Enamel  lined  digester. 
Frank,  Adolph.    376189  and  376190.    Jan.  10,  1888. 

Production  of  sulphite  solutions. 
Francke,  David  Otto.     295865.     March  25,  1884. 

Manufacture  of  paper  pulp. 
Francke,  David  Otto.     304092.     Aug.  26,  1884. 

Digester. 
Gamotis,  L.,  and  S.  Martin.     17830.    July  21,  1857. 

Apparatus  for  making  acid  sulphite  of  lime. 
Getchell,  C.  E.    378673.    Feb.  28,  1888. 

Apparatus  for  making  sulphurous  acid. 
Godfrey,  C.,  and  Reuben  Lighthall.     109508.     Nov.  22,  1870. 

Protecting  iron  against  corrosion  by  applying  to  iron  an  electropositive 
metal  or  alloy.     Same  idea  has  recently  been  proposed  for  protecting 
sulphite  digesters. 
Graham,  James  Anthony.    280466.    July  3,  1883. 

Covering  iron  with  lead. 
Graham,  James  Anthony.    280171.     June  26,  1883. 

Treating  fibrous  substances. 
Hanish,  E.,  and  M.  Schroeder.     376883.    Jan.  24,  1888. 

Obtaining  sulphurous  acid. 
Haskell,  J.  R.     63044.     March  19,  1867. 

Treating  and  separating  vegetable  fibres.     Not  on  sulphite  process,  but 
claim  covers  first  steaming  the  fibres  and  then  condensing  steam  by 
shower  of  cold  liquor  so  as  to  force  liquor  into  the  wood,  as  in  later 
patents  of  Mitscherlich. 
Hatschek,  Moritz.     101011,     March  22,  1870. 

Tower  apparatus  for  producing  sulphurous  acid. 
Hess,  J.    434272.    August  12,  1890. 

Digester. 
Horsford,  E.  N.    39922.     Sept.  15,  1863. 

Preparation  of  dry  sulphite  of  lime. 
Howell,  W.  H.    487887.    Dec'.  13,  1892. 

Liquor  apparatus. 
Hughes,  H.  A.    290642.    Dec.  18,  1883. 

Apparatus  for  preparing  sulphuretted  cream  of  lime  (sulphite  of  lime;. 
Jones,  N.  M.    See  Curtis,  Chaa. 
Jones,  W.  D.    188801.    March  27,  1877.     197474.    Nov.  27,  1877. 

Apparatus  for  manufacture  of  hydrated  sulphurous  acid. 
Kellner,  Carl  or  Charles.    See  also,  Hitter,  Eugen  Baron. 
Kellner,  Charles.    352759.    Nov.  16,  1886. 

Method  of  sizing  paper,  to  prevent  sulphite  and  ground  wood  from  turn- 
ing yellow.    He  precipitates  the  rosin  size  with  a  sulphite  salt. 
Keys,  William  W.,  and  N.  W.  Williams.    212077.     ?eb.  4,  1879. 

Deoxidized  bronze. 


4.74  THE  CHEMISTRY  OF  PAPER-MAKING* 

Keys,  William  W.    420275.    Jan.  28,  1890. 

Sectional  bronze  digester. 
Ladd,  William  P.    115327.    May  30,  1871. 

Rotary  digester  without  regard  to  psocess. 
Lavery,  R.    431267.    July  1, 1890. 

Digester. 
Little,  Arthur  D.    351330.    Oct  19, 1886. 

Enamel  lining  for  digesters. 
Lovejoy,  F.  C.    429692.    June  10, 1890. 

Digester. 
Lunge,  George.    344322.    June  22,  1880. 

Apparatus  for  treating  liquids  with  gas. 
Marr,  William.    70588.    Nov.  5,  1867. 

Manufacture  of  bisulphite  of  lime. 
Marshall,  George  R    See  Wheelwright,  Charles  S 
Marshall,  James  F.    312875.    Feb.  24, 1885. 

Digester. 
Makin,John.    335943.    Feb.  9, 18S6. 

Digester. 
Makin,  John.    344120.    June  22, 1886. 

Lead-lined  digester. 
Makin,  John.    312485.    Feb  17, 1885. 

Combined  lead  and  iron  plate. 
MarceTm,  Paul.    123713.    Feb.  13    LB72. 

'Manufacture  of  sulphurous  acid. 
Martin,  S.    See  Gamotis,  L. 
Maste,  1L  A.  A.    480334.    Aug.  9,  1892. 

Preparation  of  cellulose  from  wood. 
Maynard,  W.    309968.    Dec.  30, 1884. 

Apparatus  for  <sharging  liquids  with  gas. 
Mayixard,  W.    180901.    Aug.  8,  1876.    183185.    Oct.  10,  1876. 

Apparatus  for  manufacture  of  hydrated  sulphurous  acid. 
MeBoiigall,  Isaac  S.    298602.    May  13, 1884. 

Digester, 
MvOcaagall,  Isaac  S.    311595.     Feb.  3,  1885. 

Manufacture  of  sulphurous  acid. 
MmftatiVltoniei.    307972,    Nov.  11,  1884.    319295.    June  2, 1885. 

Treating  vegetable  fibre. 
Mit»:l»er}icli,  Alex.    395914.    Jan.  8,  1889. 

Manufacturing  thread  from  short  fibre. 
Mitscherlicli,  Alex.     263797.    Sept.  5,  1882. 

Manufacturing  of  tamiic  acid  from  waste  sulphite  liquors. 
Mitscherlich,  Alex.     284319.     Sept.  4,  1883. 

Process  and  digester. 
Mitscherlich,  Alex.    377694.    March  9,  1S86. 

Boiling  fibres  with  sulphites,    (Preparation  of  liquor,  process  of  treating 
wood.) 


APPENDIX.  475 


Mitscherlich,  Alex,    336013.     Feb.  9,  1880. 

Sizing  paper  (by  material  in  waste  liquor  from  sulphite  -boiling). 
Mitscherlich,  Alex.    3443*23.    June  22,  1886. 

Paper  pulp.     (Process  and  apparatus  for  manufacturing.) 
Montgomery,  T.  W.,  and:  J.  Warnke.     433534.    Aug.  5,  1890. 

Apparatus  for  washing  the  fumes  of  sulphur  (sulphurous  acid). 
Noble,  G.  R.    345168.    July  6, 1886. 

Making  lead-lined  digesters. 
Noble,  G.  R.    427892.    May  13,  1.800. 

Lining  boilers  with  lead. 
Norton,  J.     480934.     Aug.  1C,  1892* 

Lining  for  tanks. 
Norton,  J.    496275.    April  2&,  1893. 

Digester. 
Phillips,  George  li.     307587.    Nov.  4,  1884. 

Lining  for  digesters. 
Frctet,  R.  P.    404431.    June  4,  1889. 

Process  of  disintegrating  fibrous  materials. 
Pictet,  R.  P.    191778.    June  12,  1877. 

Apparatus  for  manufacture  of  sulphurous  anhydride. 
Pictet,  R.  P.    331323.     Dec.  1,  1885. 

Manufacture  of  pulp  from  woody  matter. 
Pond,  Goldsburg  H.    354931.    Dec.  28,  18S6. 

Manufacture  of  paper  pulp  from  wood. 
Pond,  Goldsburg  H.    351067.    Get  19,  1886. 

Machine  for  manufacture  of  wood  pulp.    Manufacture  of  bronze,  and 
its  use  in  digesters,  etc.,  to  resist  chemicals,  sulphuric  acid,  etc.,  in 
preparation  of  wood  pulp. 
Pond,  Goldsberg  H.    351068.    Oct.  19,  188G. 

Manufacture  of  wood  pulp. 
Radam,  W.    412664.    Oct.  8,  1889. 

Apparatus  for  impregnating  liquids  with  gases. 
Randon/  Francois.    337197.    March  2,  1886. 

Apparatus  for  production  of  pure  sulphurous  acid. 
Radford,  B.  P.    483942.    Oct.  4,  1892. 

Digester. 
Reynolds,  Eli  A.    423531.    March  18,  1890. 

Digester. 
Reyuoso,  A.  F.  C.     185964.    Jan.  2,  1877. 

Apparatus  for  manufacture  of  sulphurous  acid. 
RHter,  Eugen  Baron,  and  Carl  Kellner.    328812.    Oct.  20,  1885. 

Apparatus  for  manufacture  of  cellulose  from  wood. 
Ritter,  Eugen  Baron,  aitd  Qarl  Kellner.    329214.     Oct.  27,  1885. 

Apparatus  (arrangement  of  tanks  and  digesters). 
Ritter,  Eugen  Baron,  and  Carl  Keliner.    329215.    Oct.  27,  1885. 

Process  of  manufacturing  cellulose. 
Ritter,  Eugen  Baron,  and  Carl.  Kellner.    829210.    Oct.  27,  1885. 

Making  solutions  of  bisulphites. 


476  THE  CHEMISTRY  OF  PAPER-MAKING. 

Hitter,  Eugen  Baron,  and  Carl  Kellner.     329217.     Oct.  27,  1885. 

Digester. 
Hitter,  Eugen  Baron,  and  Carl  Kellner.     338557.     March  23,  1886. 

Apparatus  for  manufacture  of  sulphurous  acid. 
Hitter,  Eugen  Baron,  and  Carl  Kellner.     338558.     March  23,  1886. 

Process  for  manufacturing  sulphites. 
Russell,  G.  F.    445235.    Jan.  27,  1891. 

Digester. 
Russell,  G.  F.    Reissue,  11286.    Nov.  15,  1892. 

Digester. 
Russell,  George  W.    341434  and  341435.    May  4,  1886. 

Digester. 
Sauriders,  John.     234431.     Nov.  16,  1880. 

Slide  valve  gate  for  digesters. 
Schenck,  Garrett.     363173.     May  17,  1887. 

Process  of,  and  apparatus  for,  charging  liquids  with  gas. 
Schenck,  Garrett.     395082.     Dec.  25,  1888. 

Apparatus  for  preparing  solutions  of  bisulphites. 
Schnurmann,  Heinrich,  and  Gotthold  Closs.     360484.     April  5,  1887. 

Apparatus.     (Digester,  heater,  and  circulation  apparatus.) 
Schroeder,  M.     See  Hanish,  E. 
Smith,  Sidney.    428149.    May  20,  1890. 

Lead  lined  digester. 
Smith,  Sidney.     421201.    -Feb.  1-1,1890. 

Sulphur  burner. 
Smith,  S.    428149.    May  20,H890. 

Digester.       I 
Smith,  S.    443922.    Dec.  30,  1890. 

Digester. 
Smith,  S.    443923. «  Dec.  30,  1890. 

Digester. 
Smith,  S.    443924.    Dec.  30,  1890. 

Digester. 
Spence,  Peter.     248541.     Oct.  18,  1881. 

Furnace  for  burning  pyrites. 
Spiro,  J.     See  Wendler,  A. 
Springer,  C.  C.    411838.    Oct.  1,  1889. 

Digester. 
Springer,  C.  C.    335046.    Jan.  26,  1886. 

Digester; 
Stebbins,  Henry  W.     405279.     June  18,  1889. 

Digester. 
Tilghman.  B.  C.     70485.     Nov.  5,  1867. 

Treating  vegetable  substances  for  making  paper  pulp.     The  foundation 

patent. 
Tilghman,  B.  C.    92229.    July  6,  1869. 

Process  of  treating  vegetable  substances  to  obtain  fibre. 


APPENDIX.  477 


Tompkins,  John  D.    401609.     April  16,  1889. 

Digester. 
Turner,  Walter  J.     123799.     Feb.  20,  1872. 

Apparatus  for  manufacture  of  bisulphites. 
Wagg,  S.  R.    373703.    Nov.  22,  1887. 

Digester. 
Wagg,  S.  R.    390727.    Oct.  9,  1888. 

Lining  for  digesters. 
Wagg,  S.  R.    440242.    Nov.  11,  1890. 

Digester. 
Wagg,  S.  R.    446041.     Feb.  10,  1891. 

Digester. 
Walker,  G.  R.    310753.    Jan.  13,  1885. 

Treating  yucca  to  obtain  fibre.    Uses  borax  liquor  and  sulphurous  acid, 
Warnke,  J.    See  Montgomery,  T.  W. 
Wendler,  A.,  and  J.  Spiro.    446652. 

Liquor  apparatus. 
Wheelwright,  Charles  S.    337720.    337721.    March  9,  1886. 

Digester  or  converter. 
Wheelwright,  Charles  S.    307608.    Nov.  4,  1884. 

Digester. 
Wheelwright,  Charles  S.,  and  George  E.  Marshall.    307609.     Nov.  4,  1884. 

Apparatus  for  treating  wood. 
Williams,  N.  W.    See  Keys,  William  W. 
Wurtz,  Henry.     252287.    Jan.  10,  1882. 

Treating  pyrites  for  manufacture  of  sulphurous  acid.  :,  j 

Zier,  Michael.    See  Bremaker,  Charles. 


478  THE  CUEMISTllY  OF  PAPER-MAKING. 


METRIC   WEIGHTS    AND   MEASURES. 

For  the  complicated  system  of  weights  and  measures  in  use  in  this 
country  and  in  England,  most  chemists  substitute  the  very  simple 
metric  system.  The  unit  of  the  system  is  the  metre,  a  rod  of  plati- 
num deposited  in  the  Archives  of  France,  which,  when  constructed 
was  supposed  to  he  one  ten-millionth  part  of  the  quadrant  of  a  great 
circle  encompassing  the  earth  on  the  meridian  of  Paris. 

Measures  of  Length. — The  metre  measures  39.37  inches.  It  is 
multiplied  and  subdivided  by  10  for  the  higher  and  lower  measures 
of  length. 

Metres.  Inches. 

kilometre  1000.0  39370.0 

hectometre  100.0  3937.0 

decametre  10.0  393.70 

metre  1.0  3937 

decimetre  0.1  3.937 

centimetre  0.01  0.3937 

millimetre  0.001  0.03937 

The  Greek  prefixes  deca,  facto,  and  kilo  are  used  to  represent  the 
numbers  10,  100,  and  1000,  respectively,  and  the  Latin  dec/,  centi,  and 
mitti  signify  a  tenth,  hundredth,  and  thousandth.  The  prefixes  are 
used  with  the  same  meaning  in  the  other  measures.  The  decimetre 
is  very  nearly  4  inches  in  length.  This  affords  an  easy  method  of 
roughly  translating  measures  of  the  one  denomination  into  those  of 
the  other. 

Measures  of  Capacity.  —  The  measure  of  capacity  is  derived  from 
that  .of  length  by  taking  one  cubic  decimetre  as  the  unit.  This  is 
jiamed  the  litre,  the  capacity  of  which  and  that  of  its  derivatives  in  the 
United  States  measures  are  appended :  — 

Plats  (U.  S.). 

2113.1 
211.31 
21.131 
2.1131 
0.2113 
0.02113 
0.002113 


Litres. 

Cubic  inches. 

kilolitre 

1000.0 

61027.0 

hectolitre 

mo 

6102.7 

decalitre 

10,0 

610.27 

litre 

1.0 

61.027 

decilitre 

0.1 

6.1027 

centilitre 

0.01 

0.61027 

millilitre 

0.001 

0.061027 

APPENDIX* 


479 


The  litre  being  the  capacity  of  a  cubic  decimetre,  it  is  evident  that 
the  inillilitre  equals  in  volume  a  cubic  centimetre,  and  this  latter 
term,  or  its  abbreviation  (c.c.),  is  very  frequently  used  in  preference 
to  millilitre;  thus  a  pipette  is  said  to  contain  50  c.c,,  and  a  litre  flask 
is  often  called  a  1000  c.c.  flask. 

A  cubic  inch  is  equal  to  16.3  cubic  centimetres. 

Measures  of  Weight.  —  The  weight  of  one  cubic  centimetre  of 
distilled  water  at  its  maximum  density  ^(4°  C.)  is  taken  as  the  unit 
of  weight,  and  is  called  a  gramme  or  gram.  The  subdivision  and 
multiples  are  again  the  same. 


Avoirdupois  ounces. 

35.2739 
3.52739 
0.352739 
0.0352739 
0.003527 
0.0003527 
0.00003527 


A  kilogramme  is  a  little  over  2  Ibs.  3J  oz.,.  and  a  hectogramme 3J  oz. 
An  ounce  avoirdupois  equals  28.35  grammes. 

The  relation  between  the  weight  and  volume  of  water  is  seen  to  be 
a  very  simple  one,  the  volume  being  the  £aine  number  of  cubic  centi- 
metres  as  the  weight  in  grammes.  With  other  liquids  the  volume  in 
cubic  centimetres  x  specific  gravity  «?*  weight  in  grammes. 


kilogramme 

<*ramines. 

1000.0 

Grains. 

15432.3 

hectogramme 

100.0 

1543.23 

decagramme 

10.0 

154.323 

gramme 

1.0 

15.4323 

decigramme 

0.1 

1.5432 

centigramme 

0.01 

0.15432 

milligramme 

0.001 

0.015432 

RELATIONS   BETWEEN   THERMOMETERS. 

In  Fahrenheit's  thermometer,  the  freezing-point  of  water  is  placed; 
at  32°,  and  the  boiling-point  at  212°,  and  the  number  of  intervening 
degrees  is  180. 

The  Centigrade,  or  Celsius's  thermometer,  which  is  now  recognized 
in  the  United  States  Pharmacopoeia,  and  has  been  adopted  gener- 
ally by  scientists,  marks  the  freezing-point  0,  and  the  boiling-point 
100. 

From  the  above  statement  it  is  evident  that  180°  of  Fahrenheit  are 
equal  to  100°  oi  Centigrade ;  or,  1°  of  the  first  is  equal,  to  f  of  a  degree 
of  the  second.  It  is  easy,  therefore,  to  convert  the  degrees  of  one  to 


480 


THE  CHEMISTRY  OF  PAPER-MAKING. 


the  equivalent  number  of  degrees  of  the  other;  but  in  ascertaining  the 
-corresponding  point  of  the  different  scales  it  is  necessary  to  take  into 
consideration  their  different  modes  of  graduation.  Thus,  as  the  0  of 
Fahrenheit  is  at  32°  below  the  point  at  which  that  of  the  Centi- 
grade is  placed,  this  number  must  be  taken  into  account  in  the  calcula- 
tion. 

If  any  degree  on  the  Centigrade  scale,  either  abo^B  or  below  0,  be 
multiplied  by  1.8,  the  result  will  in  either  case  be  the  number  of 
degrees  above  or  below  32,  or  the  freezing-point,  Fahrenheit. 

The  number  of  degrees  between  any  point  on  the  Fahrenheit  scale 
and  32,  if  divided  by  1.8,  will  give  the  corresponding  point  on  the 
Centigrade. 


THERMOMKTRIC  EQUIVALENTS, 
According  to  the  Centigrade  and  Fahrenheit  Scales. 


c. 

F. 

€. 

F. 

C. 

F. 

-40 

-  -40.0 

3 

37.4 

30 

86.0 

-35 

-31.0 

4 

39.2 

31 

87.8 

-30 

-22.0 

5 

41.0 

32 

89.6 

-25 

-13.0 

6 

42.8 

33 

91.4 

-20 

-  4.0 

7 

44.6 

34 

93.2 

-.19 

-  2.2 

8 

46.4 

35 

95.0 

-18 

-  0.4 

9 

48.2 

36 

96.8 

* 

-17 

-f  1.4 

10 

50.0 

37 

98.6 

-16 

3.2 

11 

51.8 

38 

100.4 

-15 

5.0 

12 

63.6 

39 

100.2 

-14 

6.8 

13 

55.4 

40 

104.0 

-13 

8.6 

14 

57.2 

41 

1  106.8 

-12 

10.4 

16 

59.0 

42 

107.6 

-11 

12.2 

16 

60.8 

43 

109.4 

-10 

14.0 

17 

62.6 

44 

111.2 

-  9 

15.8 

18 

64.4 

45 

113.0 

-  8 

17.6 

19 

66.2 

46 

114.8 

-  7 

19.4 

20 

68.0 

47 

116.6 

-  6 

21.2 

21 

.  69.8 

48 

118.4 

-  5 

23.0 

22 

71.6 

49 

120.2 

-  4 

24.8 

23 

73.4 

50 

122.0 

-  3 

26.6 

24 

75.2 

61 

123.8 

-  2 

'  28.4 

25 

77.0 

52 

126.6 

-  1 

30.2 

26 

78.8 

63 

127.4 

0 

32.0 

27 

80.6 

54 

129.2 

+  1 

33.8 

28 

82.4 

55 

131.0 

2 

35.6 

29 

84.2 

56 

132.8 

APPENDIX, 


481 


THERMOMETBIC  EQUIVALENTS  (continued'). 


c. 

F. 

C. 

F. 

O. 

F. 

57 

134.6 

92 

197.6 

127 

260.6 

58 

136.4 

98 

199.4 

128 

262.4 

59 

138.2 

9i 

201.2 

129 

264.2 

60 

140.0 

95 

203.0 

180 

266.0 

61 

141.8 

96 

204.8 

131 

267.8 

62 

143.6 

97 

206.6 

132 

269.6 

63 

145.4 

98 

208.4 

183 

271.4 

64 

147.2 

99 

210.2 

134 

273.2 

65 

149.0 

100 

212.0 

135 

275.0 

66 

150.8 

101 

2  IS.  8 

136 

276.8 

67 

152.6 

102 

215.6 

137 

278.6 

68 

154.4 

103 

217.4 

138 

280.4 

69 

156.2 

104 

219.2 

139 

282.2 

70 

158A) 

105 

221.0 

140 

284.0 

71 

159.8 

106 

222.8 

141 

285.8 

72 

161.6 

107 

224.6 

142 

287.6 

73 

163.4 

108 

226.4 

143 

289.4 

74 

166.2 

109 

22&2 

144 

291.2 

75 

167,0 

110 

230.0 

145 

293.0 

76 

168.8 

111 

231.8 

146 

294.8 

77 

170.6 

112 

233.6 

147 

296.6 

78 

172.4 

113 

235.4 

148 

298.4 

79 

174.2 

114 

237.2 

149 

300.2 

80 

176.0 

115 

239.0 

150 

302.0 

81 

177.8 

116 

240.8 

151 

303.8 

82 

179.6 

117 

242.6 

152 

305.6 

83 

181.4 

118 

244.4 

153 

307.4 

84 

183.2 

119 

240.2 

154 

309.2 

80 

185.0 

120 

248.0 

155 

311.0 

86 

186.8 

121 

249.8 

156 

312.8 

87 

183.6 

122 

251.6 

157 

314.6 

88 

190.4 

123 

253.4 

158 

316.4 

8D 

192.2 

124 

255.2 

159 

318.2 

90 

194.0 

125 

257.0 

160 

320.0 

91 

195.8 

126 

258.8 

482 


THE  CHEMISTRY  OF  PAPER-MAKING. 


SPECIFIC  GUAVITV  CORRESPONDING  TO  DEGREES  OF  BAUME'S  HYDROMETER  FOR 
LIQUIDS  LIGHTER  THAN  WATER. 


Degree  of 
hydrometer. 

Specific  gravity. 

I)«gree  of 
hydrometer. 

Specific  gravity. 

Degree  of 
hydrometer. 

Specific  gravity. 

10 

1.000 

33 

0.862 

56 

0.758 

11 

0.993 

34 

0.857 

57 

0.754 

12 

0.983 

35 

0.852 

58 

0.760 

13 

0.979 

36 

0.847 

59 

0.746 

14 

0.973 

37 

0.842 

60 

0.742 

15 

0.966 

38 

0.837 

61 

0.738 

16 

0.960 

39 

0.832 

62 

0.735 

17 

0.953 

40 

0.827 

03 

0.731 

18 

0.947 

41 

0.823 

64 

0.727 

19 

0.941 

42 

0.818 

65 

0.724 

20 

0.935 

43 

0.813 

66 

0.720 

21 

0.929 

44 

0.809 

67 

0.716 

22 

0.923 

45 

0.804 

68 

0.713 

23 

0.917 

46 

0.800 

69 

0.709 

24 

0.911 

47 

0.795 

70 

0.706 

25 

0.905 

48 

0.731 

71 

0.702 

26 

0.900 

49 

0.787 

72 

0.699 

27 

0.894 

50 

0.783 

73 

0.696 

28 

0.889 

51 

0.778 

74 

0.692 

29 

0.883 

52 

0.774 

75 

0.689 

30 

0.878 

53 

0.770 

70 

0.686 

31 

0.872 

54 

0.766 

77 

0.682 

32 

0.867 

55 

0.762 

PERCENTAGE  OF  SODIUM  CHLORIDE  IN  Souunoss  OF  DIFFERENT  SPECIFIC 

GRAVITIES. 


Specific  gravity. 

Per  cent. 
NaCl. 

Specific  gravity. 

Per  cent. 
NaCl. 

Specific  gravity. 

Per  cent. 
JSTaCl. 

1.00725 

1 

1.07335 

10 

.14315 

19 

1.01450 

2 

1.08097 

11 

.15107 

20 

1.02174 

3 

1.08859 

12 

.15931 

21 

1.028999 

4 

1.09622 

13 

.16755 

22 

1.03624 

5 

1.10384 

14 

.17580 

23 

1.04366 

6 

1.11146 

15 

.18404 

24 

1.05108 

7 

1.11938 

16 

.19228 

25 

1.05851 

8 

1.12730 

17 

1.20098 

26 

1.06593 

9 

1.13523 

18. 

1.20433 

26.395 

APPENDIX. 


483 


SPECIFIC  GRAVITY  CORRESPONDING  TO  DEGREES  OF  BAUME'S  HYDROMETER  FOR 
LIQUIDS  HEAVIER  THAN  WATER. 


Degree  of 
hydrometer. 

Specific  gravity. 

Degree  of 
hydrometer. 

Specific  gravity. 

Degree  of 
hydrometer. 

Specific  gravity. 

0 

1.000 

26 

1.221 

52 

1.666 

1 

1.007 

27 

1.231 

53 

1.683 

2 

1.014 

28 

1.242 

64 

1.601 

3 

1.022 

29 

.252 

55 

1.618 

4 

1.029 

30 

.261 

56 

1.637 

5 

1.036 

31 

.275 

57 

1.66e 

6 

1.044 

32 

.286 

58 

1.676 

7 

1.052 

33 

.298 

69 

1.696 

8 

1.060 

34 

1.309 

60 

1.715 

9 

1.007 

35 

1.321 

61 

1.736 

10 

1.075 

36 

1.334 

62 

1.758 

11 

1.083 

37 

1.346 

63 

1,779 

13 

1.091 

36 

1.359 

64 

1.801 

13 

1.100 

39 

1.372 

65 

1.823 

14 

1.108 

40 

1.384 

66 

1.847 

15 

1.116 

41 

1.398 

67 

1.872 

16 

1.125 

42 

1,412 

68 

1.897 

17 

1.134 

43 

1.426 

69 

1.921 

18 

1.143 

44 

1.440 

70 

1.046 

19 

1.152 

45 

1.454 

71 

1.074 

20 

1.161 

46 

1.470 

72 

2.002 

21 

1.171 

47 

1.485 

73 

2,031 

22 

L180 

48 

1.501 

74 

2.069 

23 

1.190 

49 

1.516 

75 

2.087 

24 

1.199 

50 

1.532 

26 

1.210 

51 

1.549 

PERCENTAGE  OF  OXALIC  ACID  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC  GRAVITY 

AT  15°  C. 


Per  cent. 

Per  cent. 

Per  cent. 

Specific  gravity. 

C2H,O* 

Specific  gravity. 

CjHjQ* 

Specific  gravity. 

+  2     4    . 

+  2     2    . 

+  21,0. 

1.0032 

1 

1.0182 

6 

1.0271 

10 

1.0064 

2 

1.0204 

7 

1.0289 

11 

1.0096 

3 

1.0226 

8 

1.0309 

12 

1.0128 

4 

1.0248 

9 

1.0320 

12.6 

1.0160 

5 

484 


THE  CHEMISTRY  OF  PAPER-MAKING. 


SPECIFIC  GRAVITY  CORRESPONDING  TO  DEGREES  OP  TWADDLE'S  HYDROMETER. 


Degrees 
Twaddle. 

Specific 
gravity. 

Degrees 
Twaddle. 

S  peel  fie 
gravity. 

Degrees 
Twaddle. 

Specific 
gravity. 

0 

1.000 

43 

1.215 

86 

1.400 

1 

1.006 

44 

1.220 

87 

1.435 

2 

1.010 

45 

1.225 

88 

.440 

3 

1.015 

46 

1.230 

89 

.445 

4 

1.020 

47 

1.235 

90 

.460 

6 

1.025 

48 

1.240 

91 

.455 

6 

1,030 

49 

1.245 

92 

.460 

7 

1.036 

60 

1.260 

93 

.466 

8 

L040 

51 

1.255 

94 

.470 

9 

1.046 

59 

1.260 

96 

.475 

10 

1.050 

63 

1.265 

96 

.480 

11 

1.055 

54 

1.270 

97 

.485 

12 

1.060 

65 

1.276 

98 

.490 

13 

1.065 

66 

1.280 

99 

.495 

14 

1.070 

67 

1.285 

100 

.600 

15 

1.076 

68 

1.290 

101 

1.505 

10 

1.080 

59 

1.295 

102 

1.610 

17 

1.085 

60 

1.300 

103 

1.516 

18 

1.090 

61 

1.306 

104 

1.620 

19 

1.095 

62 

1.310 

105 

1.525 

20 

1.100 

63 

1.315 

106 

1.630 

21 

1.106 

64 

1.320 

107 

1.635 

22 

1.110 

66 

1.825 

108 

1.540 

23 

1.111 

66 

1.330 

109 

1.545 

24 

1.120 

67 

1.335 

110 

1.650 

25 

1.125 

68 

1.340 

111 

1.665 

26 

1.130 

69 

1.345 

112 

1.560 

27 

.135 

70 

1.850 

113 

1.565 

28 

.140 

71 

1.355 

114 

1.670 

29 

.145 

72 

1.360 

115 

1.575 

30 

.160 

73 

1.365 

116 

1.580 

31 

.155 

74 

1.870 

117 

1.585- 

82 

.160 

75 

1.375 

118 

1.590 

33 

.165 

76 

1.380 

119 

1.595 

34 

.170 

77 

1.385 

120 

1.600 

86 

1.176 

78 

1.390 

121 

1.605 

86 

1.180 

79 

1.395 

122 

1.610 

87 

1.185 

80 

1.100 

123 

1.615 

38 

1.190 

81 

1.405 

124 

1.620 

39 

1.195 

82 

1.410 

125 

1.025 

40 

1.200 

83 

1.415 

126 

1.630 

41 

1.205 

84 

1.420 

127 

1.635 

42 

1.210 

85 

1.425 

128 

1.640 

APPENDIX. 


485 


SPECIFIC  GBAVITY  CORRESPONDING  TO  DEGREES  OK  TWADDLE'S  HTDROMETEI 

{continued). 


Degrees 
Twaddle. 

Specific 
gravity. 

Degrees 
Twaddh*. 

Specific 
gravity. 

Degrees 
Twaddle. 

Specific 
gravity. 

129 

1.645 

153 

1.765 

177 

1.885 

130 

1.650 

154 

1.770 

178 

1.890 

131 

1.655 

155 

1.775 

179 

1.895 

132 

1.660 

15ft 

1.780 

180 

1.900 

183 

1.665 

157 

1.785 

181 

1.905 

134 

1.670 

158 

1.790 

182 

1.910 

135 

1.675 

159 

1.795 

183 

1.915 

138 

1.680 

160 

.800 

184 

1.920 

137 

.685 

161 

.805 

185 

1.925 

138 

.690 

162 

.810 

186 

1.930 

139 

.695 

163 

.815 

187 

1.935 

140 

.700 

164 

.820 

188 

1.940 

141 

.705 

165 

.825 

189 

1.945 

142 

.710 

166 

.830 

190 

1.950 

143 

.715 

167 

.835 

191 

1.955 

144 

.720 

168 

.840 

192 

1.960 

145 

1.725 

169 

.845 

193 

1.905 

14(5 

1.730 

170 

1.850 

194 

1.970 

147 

1.735 

171 

1.855 

195 

1.976 

148 

1.740 

172 

1.860 

196 

1.980 

149 

1.745 

173 

1.865 

197 

1.986 

150 

1.750 

174 

1.870 

198 

1.990 

151 

1.755 

175 

1.875 

199 

1.996 

152 

1.760 

176 

1.880 

200 

2.00O 

4B6 


THE  CHEMISTRY  OF  PAPER-MAKING. 


TABLE  OF  THE  ELEMENTS,  TOGETHER  WITH  THEIR  SYMBOLS  AND  APPROXIMATE 

ATOMIC  WEIGHTS.1 


Symbols. 

Atomic  weight. 

Symbols. 

Atomic  weight. 

Aluminum  .    . 

Al 

27.5 

Molybdenum  . 

Mo 

96 

Antimony    ,     . 

Sb 

122 

Nickel    .     .     . 

Hi 

59 

Arsenic   .     ,     . 

As 

75 

Niobium     .     . 

Nb 

94 

Barium   .     .     . 

Ba 

137 

Nitrogen     .     . 

N 

14 

Beryllium    .     . 

Be 

9.4 

Osmium     .     . 

Os 

199 

Bismuth  .     .     . 

Bi 

208 

Oxygen      .     . 

0 

16 

Boron     .     .     . 

B 

11 

Palladium  .     . 

Pd 

106 

Bromine  .     .     . 

Br 

80 

Phosphorus    ^ 

P 

31 

Cadmium     . 

Cd 

112 

Platinum    .     . 

Pt 

197.18 

Csesium  .     . 

Cs 

133 

Potassium  .     . 

K 

39 

Calcium  .     .     . 

Ca 

40 

Rhodium    .     . 

Rh 

104 

Carbon    .     .     . 

C 

12 

Rubidium  .     . 

Rb 

85 

Cerium    ... 

Ce 

137 

Selenium    .     . 

Se 

79 

Chlorine  .     .     . 

Cl 

35.5 

Ruthenium 

Ru 

104 

Chromium  . 

Or 

62.5 

Silicon  .     .     . 

Si 

28 

Cobalt     .     .    .. 

Co 

59 

Silver    .     .     . 

Ag 

108 

Copper    .     .    . 

Cu 

63.5 

Sodium      /  ';'..  : 

Na 

23 

Didymium  .     . 

Di 

144 

Strontium  .     . 

Sr 

87.5 

Erbium  .     .     . 

Er 

170.6 

Sulphur      .    . 

S 

32 

Fluorine  .     . 

F 

19 

Tantalium  .     . 

Ta 

182 

Gold  .... 

Au 

197 

Tellurium  .     . 

Te 

125 

Hydrogen    .     . 

H 

1 

Thallium    .     . 

Tl 

.204 

Indium    .     .    . 

In 

113 

Thorium    . 

Th 

231.5 

Iodine      .     . 

I 

127 

Tin   .... 

Sn 

118 

Iridium    .     .     . 

Ir 

193 

Titanium   .    . 

11 

48 

Iron    .     . 

Fe 

56 

Uranium    . 

Ur 

?*0 

Lanthanum 

La 

139 

Vanadium  .     . 

V 

51 

Lead  .... 

Pb 

207 

Wolframium  . 

W 

184 

Lithium  . 

Li 

7 

Yttrium      .     . 

Y 

88 

Magnesium  .     . 

Mg 

24 

Zinc.     . 

Zn 

f.5 

Manganese  .    . 

Bin 

55 

Zirconium  .     . 

2r 

90 

Mercury.  .     .     . 

Hg 

200 

The  atomic  weights  here  given  are  those  u»3d  by  Lunge  in  bin  "Alkali-MnherV Handbook.' 


APPENDIX* 


487 


TEMPERATURE  OF  SATURATED  STEAM  AT  DIFFERENT  PRESSURES. 


Pressure  per 
square  inch. 

Temperature. 
Degrees  F. 

Pressure  per 
square  inch. 

Temperature. 
Degrees  F. 

Pressure  per 
square  inch. 

Temperature. 
Degree*  F. 

I 

102.1 

34 

257.6 

68 

300.9 

o 

126.3 

35 

259.3 

69 

301.9 

3 

141.6 

36 

260.9 

70 

302.9 

4 

153.1 

37 

262.6 

71 

303.9 

5 

102.3 

38 

264.2 

72 

304.8 

0 

170.2 

39 

265.8 

73 

305.7 

7 

176.9 

40 

267.3 

T4 

306.6 

8 

182.9 

41 

268.7 

75 

307.6 

9 

188.3 

42 

270.2 

76 

308.4 

TO 

193.3 

43 

271.6 

77 

309.3 

11 

197.8 

44 

273.0 

78 

310.2 

12 

202.0 

45 

274.4 

70 

311.1 

13 

205.9 

46 

275.8 

80 

312.0 

14 

209.6 

47 

277.1 

81 

312.8 

14.7 

212.0 

48 

278.4 

82 

313.6 

15 

213.1 

49 

279:7 

83 

314.5 

16 

216.3 

50 

281.0 

84 

315.3 

17 

2-19.6 

51 

282.3 

•6 

316.1 

18 

222.4 

52 

283.5 

86 

316.9 

19 

225.3 

53 

284.7 

87 

817.8 

20 

228.0 

54 

285.9 

88 

318.6 

21 

230.6 

55 

287.1 

89 

319.4 

22 

233.1 

56 

288.2 

90 

320.2 

23 

235.5 

57 

289.3 

91 

321.0 

24 

237.8 

88 

290.4 

92 

321.7 

25 

2401 

59 

294.  (j 

93                  322.5 

26 

242.3 

60 

392,7 

94                  323.3 

27 

244.4 

61 

293.8 

95                  324.1 

28 

246.4 

62 

29.4.8 

96                  324.8 

29 

248.4 

63 

296.9 

97                  325.6 

30 

250.4 

64 

296.9 

•e 

820*3 

31 

252.2 

65 

298.0 

90 

327.1 

32 

264.1 

66 

299,0 

100 

827.9 

33 

255.1) 

67 

000.0 

488 


THE  CUEHlSTRt  OF  PAPER-MAKING. 


PERCENTAGE  OF  SULPHURIC  ACID  FOB  DIFFERENT  SPECIFIC  GRAVITIES. 


Speciftc  gravity  at  15°  C. 

Per  cent,  by  weight 
c.  p.  sulphuric  acid. 
H2804. 

Specific  gravity  at  15°  C. 

Per  cent,  by  weight 
c.p.  sulphuric  acid, 

1.00 

0.09 

1.42 

52.13 

1.01 

1.67 

1.43 

63.11 

1.02 

3.03 

1.44 

54.07 

1.03 

4.49 

1.46 

55.03 

t.04 

6.96 

1.46 

55.97 

1.05 

7.37 

1.47 

56.90 

1.06 

8.77 

1.48 

67.83 

1.07 

10.19 

1.49 

68.74 

1.08 

11.60 

1.50 

69.70 

1.09 

12.99 

1.51 

60.65 

1.10 

14.35 

1.52 

61.59 

1.11 

16.71 

1.53 

62.63 

1.12 

17.01 

1.54 

63.43 

1.13 

18.31 

1.65 

64.26 

1.14 

19.61 

1.66 

65.08 

1.15 

20.91 

1.57 

65.90 

1.16 

22.19 

1.68 

60.71 

1.17 

23.47 

1.69 

67.69 

1.18 

24.76 

1.60 

68.51 

1.19 

26.04 

1.61 

69.43 

1.20 

27.32 

1.62 

70.32 

1.21 

28.58 

1.63 

71.16 

1.22 

29.84 

1.64 

71.99 

1.23 

31.11 

1.65 

72.82 

1.24 

52.28 

1.66 

73.64 

1.25 

33.43 

1.67 

74.51 

1.26 

3457 

1.68 

75.42 

1.27 

35.71 

1.69 

76.30 

1.28 

86.87 

1.70 

£7.17 

1.29 

38.03 

1.71 

78.04 

1.30 

39.19 

1.72 

78.92 

1.81 

40.35 

1.73 

79.80 

1.32 

41.50 

1.74 

80.68 

1.33 

42.66 

1.75 

81.56 

1.34 

43.74 

1.76 

82.44 

1.35 

44.82 

1.77 

83.32 

1.36 

45.88 

1.78 

84.50 

1.37 

46.94 

1.79 

85.70 

1.38 

48.00 

1.80 

86.90 

1.39 

49.06 

1.81 

88.30 

1.40 

50.11 

1.82 

90.05 

1,41 

51.16 

1.822 

90.40 

APPENDIX. 


489 


PERCENTAGE  OF  SULPHURIC  ACID  FOR  DIFFERENT  SPECIFIC  GRAVITIES 

(continued). 


Specific  gwvity  at  15°  C. 

Per  cent,  by  weiifbt 
c.p.  sulphuric  acid, 

i£so4. 

Specific  gravity  at  16°  C. 

Per  cent,  by  weight 
c.p.  sulphuric  acid, 
jf,3<V 

1.824 

90.80 

.840 

95.60 

1.820 

91.25 

.8410 

97.00 

1.828 

91.70 

.8415 

97.70 

1.830 

92.10 

.8410 

98.20 

1.832 

92.52 

.8400 

99.20 

1.834 

93.05 

1.8390 

99.70 

1.836 

93.80 

1.8385 

99.95 

1.838 

94.60 

TABLE  SHOWING  HOW  TO  PREPARE  SULPHURIC  ACID  OF  ANY  STRENGTH  BY 
MIXING  DIFFERENT  PROPORTIONS  OF  ACID  AND  WATER. 

Column  a,  shows  bow  many  parts  of  otfof  vitriol  of  1.840  specific  gravity  (66°  B,  168°  Twaddle's) 
must-bw  mixed  with  100  parts  water,  at  15°  or  2<P,  in  order  to  obtain  an  acid  of  the  specific  gravity  b. 


a 

b 

tt 

b 

a 

b 

1 

1.009 

130 

1.456 

370 

1.723 

2 

1.015 

140 

1.473 

380 

1.727 

5 

1.035 

150 

1.490 

390 

1.730 

10 

1.060 

160 

1.510 

400 

1.733 

15 

1.090 

170 

1.530 

410 

1.737 

20 

1.113 

180 

1.543 

420 

1.740 

25 

1.140 

190 

1.556 

430 

1.743 

30 

1.165 

200 

1.568 

440 

1.746 

35 

1.187 

210 

1.580 

450 

1.750 

40 

1.210 

220 

1.593 

460 

1.754 

45 

1.229 

230 

1.606 

470 

1757 

50 

1.248 

240 

1,620 

480 

1.760 

55 

1.265 

250 

1.630 

490 

1.763 

60 

1.280 

260 

1.640 

500 

1.766 

65 

1.297 

270 

1.648 

510 

1.768 

70 

1.312 

280 

1.654 

520 

1.770 

76 

1.326 

290 

1.667 

530 

1.772 

80 

1.340 

300 

1.678 

540 

1.774 

85 

1.357 

310 

1.689 

550 

1.776 

90 

1.372 

320 

1.700 

560 

1.777 

95 

1.386 

330 

1.705 

580 

1.778 

100 

1.398 

340 

1.710 

590 

1.780 

110 

1.420 

350 

1.714 

600 

1.782 

120 

1.438 

360 

1.719 

490 


THE  CHEMISTRY  OF  PAPER-MAKING. 


PERCENTAGE  OF  NITRIC  ACID  FOR  DIFFERENT  SPECIFIC  GRAVITIES. 


Specific  gravity. 

Per  cent,  by  weight  of 
nitric  acid. 

Specific  gravity. 

Per  cent,  by  weight  of 
nitric  acid. 

1.000 

0.10 

1.215 

34.55 

1.005 

1.00 

1.220 

35.28 

1.010 

1.90 

1.225 

36.03 

1.015 

£.80 

1.230 

36.78 

1.020 

3^0 

1.235 

37.53 

1.025 

4>W 

1.240 

as.  29 

1.030 

MB 

1.245 

39.05 

1.035 

6.3S 

1.250 

39.82 

1.040 

-7.28 

1.255 

40.58 

1.045 

'£.'13 

1.260 

41.34 

1.050 

8.99 

1.265 

42.10 

1,055 

9.^4 

1.270 

42.87 

1.060 

10,68 

1.276 

43.64 

1.065 

usn 

1.280 

44,41 

h070 

12.33 

1.285 

45.18 

1.076 

13,15 

1.290 

45.65 

1.080 

13;96 

1.295 

46.7.2 

1..085 

14.74 

1.300 

47.49 

1.090 

4*i8 

1.305 

48.26 

1.095 

16:132 

1:310 

49.07 

1.100 

nja 

1.315 

49.89 

1.106 

17.«9 

1.320 

50.71 

1.110 

Msta 

1.325 

51.63 

1.115 

19.46 

1.330 

52.37 

1.  120 

20.23 

t.335 

63.22 

1.125 

:31.00 

1.340 

56.07 

1.130 

21.77 

1.8,45 

64.93 

1.135 

22.6.4 

1.350 

55  79 

1.140 

23.31 

1.366                             56.60 

1.V45 

24.1)8 

1.360 

57.57 

1.150 

£4.84 

1.365 

58.48 

1.155 

25.60 

1,370 

69.39 

1.160 

26.36 

1.375 

60.80 

1.166 

2742 

1.380 

6127 

1.170 

27,88 

1,365 

62:24 

1.1.75 

26:68 

3,500 

63.23 

1.180 

29.36 

1.365 

64.25 

1.185 

30.13 

1.400 

65.30 

1.190 

30.88 

1..405 

86:40 

1.195 

31.62 

1,WO 

67.50 

1.300 

32.36 

1.4^15 

68.63 

1..205 

8&09 

1..420 

QQW 

1.210 

33^2 

.UBtf 

7098 

APPENDIX. 


491 


PERCENTAGE  OP  NITRIC  ACID  FOR  DIFFERENT  SPECIFIC  GRAVITIES  (continued) 


Specific  gravity. 

Per  cent,  by  weight  of 
nitric  acid. 

Specific  gravity. 

Per  cent,  by  weight  of 
nitric  acid. 

1,430 

72.17 

1.504 

96.00 

1,485 

73.30 

.505 

06.39 

1.440 

74.68 

.506 

96.76 

1.445 

75.98 

.507 

97.13 

1.450 

77.28 

.508 

97.50 

1.455 

78.00 

.509 

97.84 

1.460 

79.98 

.510 

9».10 

1.465 

81.42 

1.511 

98.32 

1.470 

82.90 

1.512 

98.53 

1.475 

84.45 

1.513 

98.73 

1.480 

86.05 

1.514 

98.90 

1.485 

87.70 

1.515 

99.07 

1.400 

89.60 

1.516 

99.21 

1.495 

91.60 

1.517 

99,34 

1.500 

94.09 

1.518 

99.46 

1,501 

94.60 

1.519 

99.57 

1.502 

95.08 

1.520 

99.67 

1.503 

05.55 

PERCENTAGE  OF  HYDROCHLORIC  ACID  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC 
GRAVITIES  AT  15°  C. 


Specific  gravity 

Percent.  HCl. 

Specific  gravity. 

Per  cent.  HCl. 

Specific  gravity. 

Per  cent.  HCl. 

1.000 

0.16 

1.070 

14.17 

1.140 

27.66 

1.005 

1.15 

1.075 

15.16 

1.145 

28.61 

1.010 

2.14 

1.080 

16.15 

1.150 

29.57 

1.015 

3.12 

1.085 

17.13 

1.155 

30.65 

1.020 

4.13 

1.090 

18.11 

1.160 

SI  .62 

1.025 

5.15 

1.095 

19.06 

1.165 

32.49 

1.030 

6.15 

1.100 

20.01 

1.170 

83.45 

1.035 

7.15 

1.105 

20.97 

1.175 

34.4V, 

1.040 

8.16 

1.110 

21.92 

1.180 

35.39 

1.045 

9.16 

1.115 

22.86 

1.185 

36.31 

1.050 

10.17 

1.120 

23.82 

1.190 

37.23 

1.055 

11.18 

1.125 

24.78 

1.195 

38.*ft 

1.060 

12.19 

1.180 

25.75 

1.200 

89.11 

1,005 

13.19 

1.135 

26.70 

492 


THE  CHEMISTRY  OF  PAPER-MAKING. 


PERCENTAGE  OF  ABSOLUTE  ACKTIC  ACID  IK  ACETIC  ACID  OP  DIFFERENT 
DENSITIES.    (OUDEMAWS.)  TEMPERATURE  16°  C. 


{percent. 

Specific  gravity. 

Percent. 

Specific  gravity. 

Per  cent. 

Specific  gravity. 

100 

1.0553 

C6 

1.0717 

33 

1.0447 

99 

1.0580 

65 

1.0712 

32 

1.0486 

08 

1.0804 

C4 

1.0707 

31 

1.0424 

97 

1.0625 

63 

1.0702 

30 

1.0412 

96 

1.0644 

62 

1.0697 

29 

1.0400 

95 

1.0600 

61 

1.0691 

28 

1.0388 

m 

1.0674 

60 

1.0685 

27 

1.0376 

93 

1.0686 

69 

1.0679 

26 

1.0363 

92 

1.0696 

58 

1.0673 

25 

1.0350 

91 

1.0705 

67 

1.0666 

24 

1.0337 

90 

1.0713 

56 

1.0660 

23 

1.0324 

89 

1.0720 

55 

1.0653 

22 

1.0311 

88 

1.0726 

54 

1.0646 

21 

1.0298 

8.7 

1.0731 

53 

1.0638 

20 

1.0284 

80 

1.0736 

52 

1.0631 

19 

1.0270 

85 

1.0739 

51 

1.0623 

18 

1.0256 

84 

1.0742 

50 

1.0616 

17 

1.0242 

83 

1.0744 

49 

1.0607 

16 

1.0228 

82 

1.0746 

48 

1.0598 

15 

10214 

81 

1.0747 

47 

1.0589 

14 

1.0201 

80 

1.0748 

4G 

•  1.0580 

13 

1.0185 

79 

1,0748 

45 

1.0571 

12 

1.0171 

78 

1.0748 

44 

1.0502 

11 

1.0157 

77 

1.0748 

43 

1.0552 

10 

1.0142 

76 

1.0747 

42 

1.0543 

9 

1.0127 

75 

1.0746 

41 

1.0533 

8 

1.0113 

H 

1.0744 

40 

1.0523 

7 

1.0098 

73 

1.0742 

39 

1.0513 

6 

1.0083 

72 

1.0740 

38 

1.0502 

5 

1.0067 

7i 

1.0737 

37 

1.0492 

4 

1.0052 

70 

1:0733 

36 

1.0481 

3 

1.0037 

69 

1,0729 

35 

1.0470 

2 

1.0022 

68 

1.0725 

34 

1.0469 

1 

1.0007 

67 

1.0721 

APPENDIX. 


493 


PERCENTAGE  OF  AMMONIA  IN  SOLUTIONS  of  DIFFERENT  SPECIFIC  GRAVITIES 

AT   15°  C. 


Specific  gravity. 

Per  cent.  NHa. 

Specific  gravity. 

Per  cent.  NH8. 

Specific  gravity. 

Per  cunt.  NHj. 

0.880 

35.00 

0.025 

20.18 

0.965 

8.59 

0.8S5 

33.67 

0.930 

18.64 

0.970 

7.31 

0.800 

31.73 

0.936 

17.12 

0.975 

6.05 

0.895 

30.03 

0.940 

15.63 

0.980 

4.SO 

0.900 

28.33 

0.945 

14.17 

'0.935 

3.65 

0.005 

26.64 

0.950 

12.74 

0.990 

2.31 

0.910 

24.99 

0.955 

11.32 

0.995 

1.14 

0.016 

23.35 

0.960 

9.91 

1.000 

0.00 

0.920 

21.76 

PERCENTAGE  OF  CAUSTIC  SODA  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC  GRAVITIES 

AT  15°  C. 


Specific  gravity. 

Per  cent. 
NaOH. 

Specific,  gravity. 

Per  cent. 
NnOH. 

Specific  gravity. 

Per  cent. 
NaOH. 

1.007 

0.61 

1.142 

12.64 

1.308 

27.80k 

1.014 

1.20 

1.152 

13.65 

1.320 

28;  83 

1.022 

2.00 

1.162 

14.37 

1.332 

20:98 

1.029 

2.71 

1.171 

15.13 

1.345 

31.22 

1.036 

3.35 

1.180 

15.91 

1.357 

32:47 

1.045 

4.00 

1.190 

16.77 

1.370 

33.69 

1.052 

4.04 

1.200 

17.67 

1.383 

34,96 

1.060 

629 

1.210 

18.58 

1.397 

38125 

1.067 

5.87 

1  .220 

19.68 

1.410 

37,47 

1.076 

6.65 

1.231 

20.59 

1.424 

38-.80 

1.083 

7.31 

1.241 

21.42 

1.438 

39.99 

1.091 

'    8.00 

1.252 

22.64 

1.453 

41.4rl 

1.100 

8.68 

1.263 

23.67 

1.468 

42.83 

1.108 

9.42 

1.274 

24.81 

1.498 

4&15 

1.116 

10.06 

1.285 

25.80 

1.614 

47.60 

1.125 

10.97 

1.297 

26.83 

1.630 

49.02 

1.134 

11.84 

494 


THE  CHEMISTRY  OF  PAPER-MAKING. 


PERCENTAGE  OF  SODIUM  CARBONATE  IN  SOLUTIONS  OP  DIFFERENT  SPECIFIC 
GRAVITIES  AT  15°  C. 


Specific  gravity. 

Per  cent.  Na,COs 

Per  cent.  Na2CO3  +  10  HZO 
(soda  crystals). 

1.007 

0.67 

1.807 

1.014 

1.33 

3.587 

1.022 

2.09 

5.637 

1.029 

2.76 

7.444 

1.036 

3.43 

9.251 

1.045 

4.29 

11.670 

1.052 

4.94 

13.323 

1.080 

5.71 

15.400 

1.067 

6.37 

17.180 

1.075 

7.12 

1Q.203 

1.083 

7,88 

21.252 

1.091 

8.62 

23.248 

1.100 

S.43 

25.432 

1.108 

10.19 

27.482 

1.116 

10.96 

29.632 

1.125 

11.81 

31.851 

1.134 

12.61 

34.009 

1.142 

13.16 

35.493 

1.152 

14.24 

38.405 

PERCENTAGE  OF  ACETATE  OF  LEAD  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC 
GRAVITIES  AT  15°  C. 


Specific  gravity. 

Per  cent. 

(cf3'%i5Pk 

Specific  gravity. 

Per  cent. 
(C,Hs02uPb 
+  3  HjO. 

Specific  gravity. 

Per  cent. 

(CW 

1.0127 

2 

1.1384 

20 

1.2768 

& 

1.0266 

4 

1.1544 

22 

1.2966 

S&i 

1.0386 

6 

1.1704 

24 

1.3163 

40 

1.0520 

8 

1.1869 

26 

1.3376 

42 

1.0654 

10 

1.2040 

28 

1.3588 

4-1 

1.0796 

12 

1.2211 

30 

1.3810 

40 

1.0939 

14 

1.2395 

32 

1.4041 

48 

1.1084 

16 

1.2578 

34 

1.4271 

50 

1.1234 

18 

APPENDIX. 


PERCENTAGE  OF  CAUSTIC  POTASH  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC 
GRAVITIES  AT  16°  C. 


Specific  gravity. 

Per  cent.  KOH. 

Specific  gravity. 

Per  cent.  KOH^ 

1.007 

0.9 

1.252 

27.0 

1*014 

1.7 

1.263 

28.0 

1.022 

2.0 

1.274 

29.9 

1:029 

3.6 

1.285 

29.B 

1.037 

4.4 

1.297 

30.7 

1<045 

6.0 

1.308 

31,8 

1,052 

6.4 

1.320 

32.7 

1:000 

7.4 

1.332 

33L7 

1:007 

8.2 

1.345 

34,0 

1:075 

9.2 

1.357 

35,9 

1.083 

10.1 

1.370 

36.9 

L091 

10.9 

1.383 

37.8 

i.lOO 

12.0 

1.397 

88.9 

i:ios 

1&9 

1.410 

39.9 

1.116 

13.8 

1.424 

40.9 

1.125 

14.8 

1.438 

42.1 

1.134 

15.7 

1.453 

43.4 

1;142 

16.5 

1.468 

44:6 

1U52 

17.6 

1\483 

45.8 

1:102 

l8.6 

£498 

47.1 

1-.171 

19.5 

i.514 

48.3 

1.1BO 

20.5 

J.63Q 

49/4 

1.190 

21.4 

1.546 

50.e 

1.200 

22.4 

1.663 

61.9 

1.210 

23.3 

1.580 

53.2 

1:220 

24.2 

1.597 

64.5 

1.231 

26.1 

1.615 

66.9 

1.241 

26.1 

1.634 

57.6 

PER  CENT.  OF  POTASH  ALUM  (CRYSTALS)  IN  SOLUTIONS  OF  DIFFERENT 
SPECIFIC  GRAVITY  AT  17.5°  C. 


Specific  gravity. 

Per  cent.  alum. 

Specific  gravity. 

Per-cent.  alum. 

1.007 

1 

1.022 

4 

1.010 

2 

1.027 

5 

1.017 

3 

11032 

6 

496 


THE  CBEMISTRY  OF  PAPER-MAKING. 


DENSITY  AND  COMPOSITION  OF  ALUMINIUM  SULPHATE  SOLUTIONS  (CHEMICALLY 
PURE).    TEMPERATURE  15°  C. 


Specific  gravity. 

1 

100  kilo*  tf  solution  contain  kilos. 

100  litres  of  solution  contain  kilos. 

Al,0,. 

SO,. 

Sulphate  with  13 
per  cent.  Al.Oj. 

Sulphate  with  14 
per  cent.  AISO3. 

Sulphate  with  15 
per  cent.  AljOv 

AU/V 

SO,. 

Bulphote  with  13 
per  cent.  AI2O3. 

« 

I1 

p 

*rf 
«* 

6 

*& 

05 

1.005 

0.7 

0.14 

0.32 

1.1 

1.0 

0.9 

0.14 

0.33 

1.1 

1 

0.9 

1.910 

1.4 

0.27 

0.64 

2.1 

2.0 

1.8 

0.28 

0.65 

2.2 

2 

1.0 

1.016 

2.1 

0.41 

0.95 

3.1 

2,0 

2.7 

0.42 

0.98 

3.2 

3 

2.8 

1.021 

2.8 

0.55 

1.27 

4.2 

8.9 

3.6 

0.66 

1.31 

4.3 

4 

3.7 

1.026 

3.6 

0.68 

1.59 

6.3 

4.9 

4.6 

0.70 

1.63 

6.4 

5 

4.7 

1.031 

4.2 

0.81 

1.89 

6,3 

5.8 

5.4 

O.S4 

1.96 

6.6 

6 

6.6 

1.036 

4.8 

0,94 

2.20 

7.3 

6.7 

6.8 

0.98 

2.28 

7.5 

7 

6.5 

1.040 

5.4 

1.07 

2.50 

8.3 

7.7 

7.2 

1.12 

2.61 

8.6 

8 

7.5 

1.045 

6.1 

1.20 

2.80 

9.3 

8.6 

8.0 

1.20 

2.94 

0.7 

9 

8.4 

1.050 

6.7 

1.33 

3.11 

10.3 

9.5 

8.9 

1.40 

8.26 

10.8 

10 

0..S 

1.055 

7.8 

1.46 

3.40 

11.3 

10,4 

9:1 

1.54 

3.59 

11.8 

11 

10.3 

1.059 

7.0 

1.68 

3,09 

12.2 

11.3 

10.6 

1.68 

3.91 

12.9 

12 

11.2 

1.064 

8.5 

1.71 

8.98 

13.1 

12.2 

11.4 

1.82 

4.24 

14.0 

13 

12.1 

1.068 

9.1 

1.83 

4.27 

14.1 

13.1 

12.2 

1.96 

4.57 

15.1 

14 

13.1 

1.073 

9.7 

1.96 

4.66 

15.1 

14LO 

13.1 

2.10 

4.89 

16.2 

15 

14.0 

1.078 

10.3 

2.08 

4.84 

16.0 

14.8 

13.9 

2.24 

6.22 

17.2 

16 

14.9 

1.082 

10.9 

2.20 

6.12 

16.9 

15.7 

14.6 

2.38 

5.55 

18.3 

17 

15.0 

1.087 

11.4 

2.32 

6.40 

17.8 

16.5 

15.4 

2.58 

5.87 

19.4 

18 

16:8 

1.092 

12.0 

2.44 

6.67 

18.7 

17.4 

16.2 

2.66 

6.20 

20.5 

10 

17.7 

1.096 

12.6 

2.65 

6.96 

19.7 

18.3 

17.0 

2.80 

6.52 

21.6 

20 

18.7 

1.101 

13.1 

2.67 

0.22 

20.5 

19.1 

17.8 

2.94 

6.85 

22.6 

21 

10.6 

1.105 

13.7 

2.78 

6.49 

21.4 

19.9 

18.6 

3.08 

7.18 

23.7 

22 

20.6 

i.iio 

14.2 

2.90 

6.70 

22.3 

20.7 

19.3 

3.22 

7.60 

24.8 

23 

21.6 

1.114 

14.7 

3.01 

7.02 

23.2 

21.5 

20.1 

3.36 

7.83 

25.9 

24 

22.4 

1.119 

15.8 

3.13 

7.29 

24.1 

22.4 

20.9 

3.60 

8.16 

26.0 

26 

23.3 

1.123 

15.8 

3.24 

7.55 

24.9 

23.1 

21.6 

3.64 

8.48 

28.0 

26 

24.3 

1.128 

16.3 

3.35 

7.81 

25.8 

23.9 

22.3 

3.78 

8.81 

29.1 

27 

25.2 

1.132 

16.8 

3.46 

8.06 

26.6 

24.7 

23.1 

.3.92 

9.13 

30.2 

28 

26.1 

1.137 

17.4 

8.57 

8.32 

27.5 

25.5 

23.8 

4.06 

9.46 

31.2 

29 

27.1 

1.141 

17.9 

3.68 

8.58 

28,3 

26.3 

24.5 

4.20 

9.79 

32.3 

80 

28.0 

1.145 

18.3 

3.79 

8.83 

29.1 

27.1 

25.3 

4.34 

10.11 

33.4 

31 

28.9 

1.160 

18.8 

3.89 

9.07 

30.0 

27.8 

26.0 

4.48 

10.44 

34.5 

32 

29.9 

1.154 

19.2 

4.00 

9.32 

30.8 

28.6 

26.7 

4.64 

10.76 

35.5 

33 

30.8 

1.150 

19.7 

4.11 

9.57 

31.6 

29.8 

27.4 

4.76 

11.09 

36.6 

34 

31.7 

1.163 

20.1 

4.21 

9.82 

32.4 

301 

28.1 

4.90 

11.42 

37.7 

36 

32.7 

1.168 

20.6 

4.32 

10.06 

33.2 

30.8 

28.9 

6.04 

11.74 

38.8 

m 

33.6 

1.172 

21.1 

4.43 

10.29 

34,0 

31.6 

29.6 

5..18 

12.07 

39.9 

37 

34.5 

1.176 

21.6 

4.52 

10.63 

34.8 

32,3 

30.1 

6.32 

12.40 

40.9 

38 

S5.6 

1.181 

22.1 

4.62 

10.77 

35.6 

33.0 

30.8 

5.46 

12,72 

42.0 

39 

36.4 

497 


DENSITY  AHD  COMPOSITION  OF  ALUMINIUM  SULPHATE  SOLUTIONS  (continued). 


i 

{ 

100  kilo*  of  solution  contain  kilos. 

100  litres  of  solution  contfin  kilos. 

A1.0,. 

30,. 

Sulphate  with  13 
per  cent.  Ai,Os. 

Sulphate  with  U 
per  cent.  AJ,O,. 

Sulphate  with  15 
per  cent.  Al/V 

Al,08, 

so,. 

Salphate  with  13 
per  cent.  A1,O3. 

si 

Salphate  with  15 

per  cant.  A1,O3. 

1.185 

22.5 

4.72 

n.oi 

36.8 

33.7 

31.6 

6.60 

18.06 

43.1 

40 

87.3 

1.190 

23.0 

4.82 

11.24 

37.1 

34.5 

32.2 

5.74 

13.38 

44.2 

41 

38.3 

1.194 

23.4 

4.92 

11.47 

37.9 

35.2 

32.8 

6.88 

13.70 

45.2 

42 

39.2 

1.198 

23.8 

5.02 

11.70 

38.6 

35.9 

33.5 

6.02 

14.03 

46.3 

43 

40.1 

1.203 

24.3 

6.12 

11.93 

39.4 

36.6 

34.1 

6.16 

14.35 

47.4 

44 

41.1 

1.207 

24,7 

5.22 

12.16 

40.2 

37.3 

34.8 

6.30 

14.68 

48.6 

45 

42.0 

1.211 

25.2 

5.32 

12.39 

40.9 

38.0 

35.4 

6.44 

15.01 

49.5 

46 

42.9 

1.216 

265 

6.41 

12.61 

41.6 

38.7 

36.1 

6.58 

16.33 

50.6 

47 

43.9 

1.220 

26.9 

5.51 

12.83 

42.4 

39.3 

36.7 

6.72 

15.66 

61.7 

48 

44.8 

1.224 

20.3 

6.60 

13.06 

43.1 

40.0 

37.4 

6.86 

15.99 

52.8 

49 

45.7 

1.228 

26.7 

5.70 

13.28 

43.0 

40.7 

38.0 

7.00 

16.31 

63.9 

60 

46.7 

1.232 

27.1 

6.79 

13.50 

44.6 

41.4 

38.6 

7.14 

16.64 

64.9 

61 

47.6 

1.236 

27.5 

6.89 

13.72 

45.3 

42.1 

39.3 

7.28 

16.96 

66.0 

52. 

48.5 

1.240 

27.9 

5.98 

13.94 

46.0 

42.7 

39.9 

7.42 

17.29 

57.1 

53 

49.5 

1.244 

28.3 

6.08 

14.16 

46.7 

43.4 

40.5 

7.56 

17.62 

68.2 

54 

50.4 

2.24* 

28.6 

6.17 

14.38 

47.5 

44.1 

41.1 

7.70 

17.94 

69.2 

55 

61.3 

1.262 

29.0 

6.26 

14.69 

48.2 

44.7 

41.7 

7.84 

18.26 

60.3 

56 

52.3 

1.256 

29.4 

6.35 

14.80 

48.9 

45.4 

42.8 

7.98 

18.59 

61.4 

57 

63.2 

1.261 

29.8 

6.44 

15.01 

49.5 

46.0 

42.9 

8.12 

18.92 

62.5 

58 

64.1 

1.265 

30.2 

6.63 

15.22 

60.2 

46.7 

43.5 

8.26 

19.25 

63.5 

69 

65.1 

1.269 

30.5 

6.62 

16.43 

50.9 

47.3 

44.1 

8.40 

19.57 

64.6 

60 

66.0 

1.278 

30.9 

6.71 

16.63 

61.6 

47.9 

44.7 

8.54 

19.90 

65.7 

61 

56.9 

1.277 

31.2 

6.80 

15.84 

52.3 

48.6 

46.3 

8.68 

20.23 

66.8 

62 

67.9 

1,281 

31.6      6.89 

16.04 

63.0 

49.2 

45.9 

8.82 

20.65 

67.9 

68 

68.8 

1285 

81.9      6.97 

16.26 

53.7 

49.8 

46.5 

8.96 

20.88 

68:9 

64 

69.7 

1.289 

32.3      7.06 

16.46 

64.3 

50.5 

47,1 

9.10 

21.20 

70.0 

65 

60.7 

1.293 

32.6 

7.15 

16.66 

66.0 

51.1 

47.7 

9.24 

21.53 

71.1 

66 

61.6 

1.297 

83.0 

7.23 

16.85 

66.6 

61.7 

48.2 

9.38 

21.86 

72.2 

67 

62.6 

1.301 

33.3 

7.32 

17.05 

66.3 

62.3 

48.8 

9.52 

22.18 

78.2 

68 

68.5 

1.305 

33.7 

7.40 

17.25 

67.0 

52.9 

49.4 

9.66 

22,61 

74.8 

69 

64.4 

1.309 

34.0 

7.49 

17.45 

67.6 

53.5 

49.9 

9.80 

22.84 

76.4 

70 

66.3 

1.312 

34.4 

7.67 

17.65 

58.3 

54.1 

50.5 

9.94 

23.16 

76.6 

71 

66.3 

1.316 

34.7 

7.66 

17.84 

68.9 

64.6 

61.1 

10.08 

23.49 

77.5 

72 

67.2 

1.320 

35.0 

7.74 

18.04 

59.6 

66.3 

61.6 

10.22 

23.81 

78.6 

78 

68.1 

1.324 

35.3 

7.83 

18.23 

60.2 

55.9 

52.2 

10.36 

24.14 

79.7 

74 

69.1 

1.328 

85.6 

7.91 

18.43 

60.8 

56.5 

52.7 

10.60 

24.47 

80.8 

75 

70.0 

1.831 

36.9 

7.99 

18.62 

61.6 

57.1 

53.3 

10.64 

24.79 

81.8 

76 

70.9 

1.335 

36.2 

8.07 

18.81 

62.1 

67.7 

53.8 

10.78 

26.12 

82.9 

77 

71.9 

1.339 

36.5 

8.16 

19.00 

62.7 

68.3 

54.4 

10.92 

26.45 

84.0 

78 

72.8 

498 


THE  CHEMISTRY  OF  PAPER-MAKING. 


OP    DlSTK    IN   SOLUTIONS   OF   MjLK   OP   LlME    OF   DIFFERENT    SPECIFIC 

GRAVITIES. 


Specific  unvity. 

t3ramme«  CnO 
in  1  litre. 

Specific  gravity. 

Grammes  CaO 
in  1  litre. 

Specific  gravity. 

Grammes  CaO 
iu  1  litre. 

1.01 

11.7 

1.10 

126.0 

Ivl8 

229.0 

1.02 

24.4 

1.11 

138.0 

1.18 

242.0 

1,03 

37.1 

1.12 

152.0 

1.20 

255.0 

1.04 

40.8 

1.13 

164.0 

1.21 

268.0 

1.05 

62.6 

1.14 

177.0 

1.22 

281.0 

1.00 

75.2 

1.15 

190.0 

1.23 

294.0 

1.07 

87.9 

1.16 

203.0 

1.24 

307.0 

1.08 

100.0 

1.17 

216.0 

1.25 

321.0 

1.09 

113.0 

PERCENTAGE  or  GLYCERINE  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC  GRAVITIES. 


Specific  gravity, 

Percent. 

glycerine. 

Specific  gravity. 

Per  cent, 
glycerine. 

Specific  gravity. 

Per  cent, 
glycerine. 

1.0123 

5 

lilS20 

SO 

1.2265 

84 

1.0245 

10 

1.1455 

65 

1.2318 

86 

1,0674 

15 

1.1582 

60 

1.2372 

88 

1.0498 

20 

1.1733 

65 

1.2425 

90 

1.0635 

25 

1.T889 

70 

1.2478 

92 

1.0771 

30 

1.2016 

75 

1.2531 

94 

1.0007 

36 

1.210ft 

78 

1.2584 

96 

1.1045 

40 

1.2159 

80 

1.2637 

98 

1.1183 

45 

1.2212 

82 

1.2691 

100 

S$HCi¥ic  GRAVITY  OF  DWFERENT  SOLUTIONS  or  SLLPBUROCS  ACID  IN  WATER. 


Percent,  SO,. 

8^iVc.vi* 

Pet  cent.  SO,. 

Specific  gravity 
•tlfiSc. 

Per  cent.  8O». 

Specific  gravity 
at!5*C. 

0.5 

1,0028 

4.0 

1.0221 

7.5 

1.0401 

1.0 

1.0066 

4.5 

1.0248 

8.0 

1.0426 

-L5 

1.0086 

5.0 

1.0275 

8;5 

1.0450 

2.0 

1.0113 

5.5 

1.0302 

9.0 

1.0474 

2.6 

1.0141 

6.0 

1.0328 

9.5 

1.0497 

3.0 

1.0168 

6.5 

1.0353 

10.0 

1,0520 

3.6 

1.0194 

7A) 

1.0377 

APPENDIX. 


499 


PER  CENT.  OF  CALCIUM  CHLOBIDE  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC 
GRAVITIES  AT  15°  C. 


Specific  gravity. 

Per  cent. 
CaCl2. 

Specific  gravity. 

Per  cent. 
CaCI,. 

Specific  gravity. 

Per  cent. 
CaCI,. 

1.009 

1 

1.134 

15 

1.277 

29 

1.017 

2 

1.143 

16 

1.288 

30 

1.026 

3 

1.153 

17 

1.299 

31 

1.034 

4 

1.163 

18 

1.310 

32 

1.043 

6 

1.173 

19 

1.822 

33 

1.051 

6 

1.182 

20 

1.333 

34 

1.060 

7 

1.193 

21 

1.344 

35 

1.069 

8 

1.203 

22 

1.356 

36 

1.078 

9 

1.213 

23 

1.368 

37 

1.087 

10 

1.223 

24 

1.380 

ss 

1.096 

11 

L234 

25 

1.392 

39 

1.106 

12 

1.246 

26 

1.403 

40 

1.115 

13 

1.255 

27 

1.411 

40.661 

1.124 

14 

1.266 

28 

mother  liquor. 


PERCENTAGE  OF  ALCOHOL  FOR  DIFFERENT  SPECIFIC  GRAVITIES. 


Specific  gravity 
at  15.5°  C. 
(OP  R). 

Per  cent,  by 
weight  of  abso- 
lute alcohol. 

Per  cent,  by 
vol  u  me  of  abso- 
lute alcohol. 

Specific  gravity 
at  15.5°  C. 
(60*  F.). 

Per  cent,  by 

weight  of  abso- 
lute alcohol. 

Per  cent,  by 
volume  of  abso- 
lute alcohol. 

1.000 

0.00 

0.00 

0.972- 

19.67 

24.08 

0.998 

0.79 

0.99 

0.970 

21.31 

26.04 

0.996 

2.28 

2.86 

0.968 

22.85 

27.86 

0.994 

3.41 

4.27 

0.966 

24.38 

29.67 

0.992 

4.62 

6,78 

0.964 

25.86 

31.40 

0.990 

5.87 

7.32 

0.962 

27.21 

32.98 

0.988 

7.27 

9.04 

0.960 

28.66 

34.54 

0.986 

8.64 

10.73 

0.958 

29.87 

36.04 

0.984 

10.08 

12.49 

0.950 

31.00 

37.84 

0.982 

11.62 

14.37 

0.954 

32.26 

38.75 

0.980 

13.15 

16.24 

0.952 

33.47 

40,14 

0.978 

14.82 

18.25 

0,950 

34.52 

41.32 

0.976 

16.46 

20.24 

0.948 

35.50 

42.40 

0.974 

18.08 

22.18 

0.946 

36.56 

43.60 

500 


THE  CHEMISTRY  OF  PAPER-MAKING. 


PERCENTAGE  OF  ALCOHOL  FOR  DIFFERENT  SPECIFIC  GRAVITIES  (continued). 


Specific  gravity 
at  16.50  c. 
(W°F.). 

Per  cent,  by 

weight  of  al>HO- 
1ft  te  alcohol. 

Per  cent,  by 
volume  of  aboo. 
lute  alcohol. 

8peaf?5°5?IS:ity 
(60°  P.). 

Per  cent,  by 
weight  of  abso- 
lute alcohol. 

Per  cent,  by 
volume  of  abso- 
lute alcohol. 

0.944 

37.67 

44.79 

0.866 

72.52 

79.12 

0.942 

38.78 

46.02 

0.864 

73.38 

79.86 

0.940 

39.80 

47.13 

0.862 

74.23 

80.60 

0.988 

40.80 

48.21 

0.860 

75.14 

81.40 

0.936 

41.80 

49.29 

0.858 

76.04 

82.10 

0.934 

4fi,76 

60.31 

0.866 

76.88 

82.90 

0.932 

43.71 

51.32 

0.864 

77.71 

83.60 

0.930 

44.64 

52.29 

0.852 

78.52 

84.27 

0.928 

45.55 

53.24 

0.850 

79.32 

84.93 

0.926 

46.46 

54.19 

0.848 

80.13 

86.69 

0.924 

47.36 

65.13 

0.840 

80.96 

80.28 

0.922 

48.27 

66.07 

0.844 

81.76 

86.93 

0.920 

49.16 

56.98 

0.842 

82.54 

87.65 

0.918 

50.09 

58.92 

0.840 

88.31 

88.16 

0.916 

50.98 

58.80 

0.838 

84.08 

88.76 

0.914 

61.79 

69.63 

0.836 

84.88 

89.39 

0.912 

52.68 

60.52 

0.834 

85.66 

89.99 

0.910 

g33>7 

61.40 

0.832 

86.42 

90.58 

0.908 

54.48 

62.31 

0.830 

87.19 

91.17 

0.906 

55.41 

63.24 

0.828 

87.96 

91.76 

0.904 

56.32 

64.14 

0.826 

88.76 

92.36 

0.902 

57.21 

66.01 

0.824 

89.54 

92.94 

0.000 

58.05 

65.81 

0.822 

90.29 

93.49 

0.898 

58.95 

66.69 

0.820 

91.00 

94.00 

0.896 

59.83 

67.53 

0.818 

91.71 

94.51 

0.894 

60.37 

68.33 

0.816 

92.44 

95.03 

0.892 

61.50 

69.11 

0.814 

93.18 

95.55 

0.890 

62.36 

69.92 

0.812 

93.92 

96.08 

0.888 

65.26 

70.77 

0.810 

94.62 

96.55 

0.886 

64.13 

71.68 

0.808 

96.32 

97.02 

0.884 

65.00 

72.38 

0.806 

96.03 

97.61 

0.832 

65.83 

73.16 

0.804 

96.70 

97.94 

0.880 

66.70 

73.93 

0.802 

97.37 

98.37 

0.878 

67.54 

74.70 

0.800 

98.03 

98.80 

0.876  ^ 

68.38 

75.46 

0:798 

98.66 

99.16 

0.874 

69.21 

76.20 

0.796 

99:29 

99.56 

0.872 

70.04 

76.94 

0.794 

99.94 

99.96 

0.870 

70.84 

77.64 

0.7&38 

100.00 

100.00 

0.868 

71.67 

78.36 

APPENDIX. 


501 


PER  CBNT.  or  MAGNESIUM  CHLORIDE  IN  SOLUTIONS  OF  DIFFERENT  SPECIFIC 
GRAVITIES  AT  15C  C. 


iM^-a»-.—     i    i 

Specific  gravity. 

Per  cent. 
MgCI,. 

Specific  gravity. 

Per  cent. 
MgCl2. 

Specific  gravity. 

Per  cent. 
MgClr 

1.008 

1 

1.113 

13 

1.228 

25 

1.017 

2 

1.122 

14 

1.238 

26 

1.026 

3 

1.181 

16 

1.248 

27 

1.034 

4 

1.140 

16 

1.259 

28 

1.042 

5 

1.150 

17 

1.269 

29 

1.052 

6 

1.159 

18 

1.279 

30 

1.000 

7 

1.169 

19 

1.290 

81 

1.008 

8 

1.178 

20 

1.301 

82 

1.077 

9 

1.188 

21 

1.312 

33 

1.080 

10 

1.198 

22 

1.823 

34 

1.095 

11 

1.208 

23 

1.334 

35 

1.104 

12 

1.218 

24 

BIBLIOGRAPHY. 

ABCBER,  T.  C.  —  British  Mfg.  Industries.    Vol.  8.     Manufacture  oji  Paper. 
—•Ibid.,  Vol.  15.    The  Industrial  Classes  and  Industrial  Statistics.    Paper 

and  Paper-making. 
ARXOT.  —  Technology  of  the  Paper  Trade, (Cantor  Lecture,  Society  of  Arts), 

London,  1877. 
BRIQUET,  C.  M.  —  Papiers  et  filigranes  des  archies  de  Genes.    1154-1700. 

Geneva,  1888. 
CHRISTY,  THOMAS.  —  New  Commercial  Plants  aud  Drugs,  No.  6,  Part  L, 

Fibres,    London,  1882. 
CLAPPERTON,  GEORGE.  —  Practical  Paper-making.      London,   1894.      Crosby 

Lockwood  &  Son. 
CROSS,  G.  F.  —  Report  on  Miscellaneous  Fibres.     London,  1886.     William 

Clowes  &  Sons. 
CROSS  AND  BEVAN.  —  Report  on  Pictet-Brelaz  Process.    London,  1887.    E.-  & 

F. N.  Spon. 

-Cellulose.    London,  1885.    George  Kenning. 
Chemistry  of  Hypochlorite  Bleaching.     Jour.  Soc.  Chem.  lud.,  May  31, 

18RO.  * 

Chemistry  of  Bast  Fibres.    Manchester,  1880.    Palmer  &  Howe. 
Reports  on  Hermite  Process.     London,  1886. 
A  Text-book  of  Paper-making.    London,  1888.    E.  &  F.  N.  Spon. 
Report-on  Indian  Fibres  and  Fibrous  Substances.    Londou,  1887.    E.  &  F, 
N.  Spon. 


502  THE  CHEMISTRY  OF  PAPER-MAKING. 

DAVIS,  CHARLES  THOMAS.  —  The  Manufacture  of  Paper,   Phila.,  1886.    Henry 

Carey  Baird  &  Co. 

DUNBAR,  J. —  The  Practical  Paper-maker.    London,  1881. 
FORESTRY  AND  FOREST  PRODUCTS.    Edinburgh,  1884. 
GARCON,  JULES.  —  Bibliographie  de    la    Technologic   Chimique  des    Fibres 

Textiles.    Paris,  1893.    Gauthier-Villars  et  Fils. 
GRIFFIX,  MARTIN  L.  —  Remarks  on  Chemistry  of  Sulphite  Processes.    Trans, 

Amer.  Soc.  C.  E.,  417.    1889. 

HERZBERG,  W.  —  Papier-Priifung.    Berlin,  1888.    Julius  Springer. 
HOFMANN,  CARL.  —  A  Treatise  on  Paper-making.    Phila.,  1878.    New  and 

much  enlarged  edition,  Howard  Lockwood  &  Co.,  New  York.     (In  press.) 
HOHNEL,  FRANZ  vox.  —  Die  Mikroskopie  der  technish  verwendeten  Faserstoffe. 

Vienna,  1887.     Hartleben. 
HOYER,  EGBERT.  —  Fabrikation  des  Papiers.    Brunswick,  1886.    F.  Vieweg  & 

Sohn. 
JAGEXBERG,    FERDIXAXD,  —  Die    Thierische    Leimung  fiir  endloses    Papier. 

Berlin,  1878.    Julius  Springer. 
JAPANESE  PAPERS.  —  Boston  Public  Library.    *  5024-18  contains  81  specimens 

of  plain  and  tinted  papers ;  *  5024-20  has  64  specimens  of  ornamented 

papers. 

LE  NORMANP,  L.  S»  —  Manuel  du  Fabricant  des  Papiers.    Paris,  1834. 
MICHAELIS,  MAJOH  O.  E.  —  Lime  Sulphite  Fibre  Mfg.  in  U.  S.    Trans.  Amer. 

Soc.  C.  E.,  417.    1889. 

MIERZINSKI,  S.  -—  Handbuch  der  Papiar-fabrikation.    Vienna,  1886. 
MULLER,   DR.  A.  —  Die  Bestimmung  des  Holzschliffes  iin   Papier.      Berlin, 

1887.    Julius  Springer. 
MULLER,    DR.'  L.  —  Die    Fabrikation    des    Papiers.     Berlin,   1877.     Julius 

Springer. 

MULLER,  HUGO.  —  Die  Pflanzenfaser.    Leipzig,  1873. 
MURRAY,  J.  —  Practical  Remarks  on  Modern  Paper.    Edinburgh,  1829. 
NORMAL-PAPIER.  —  Pub.  by  Die  Papier-Zeitung.    Berlin,  1891. 
PARKINSON,  R.  —  A  Treatise  on  Paper.    Preston,  1886. 
PATENTS,  BRITISH.  —  Abridgements  of  specifications  relating  to  Paper.    1636- 

1876. 

PLANCHE,  G.  —  LTndustrie  de  la  Papeterie.    Paris,  1853. 
PROTEAUX.  —  The  Manufacture  of  Paper  and  Boards.     Phila.,  1873. 
ROUTLEDGE,  THOMAS. — Bamboo  as  a  Paper-making  Material.    London,  1875. 

E.  &  F.  N.  Spon. 
SADLTER,  SAMUEL  P.  —  Industrial  Organic  Chemistry,    pp.  262-291.    Phila., 

1892.    J.  B.  Lippincott  Co. 

SARGEANT,  CHARLES  S,  —  Forest  Trees  of  North  America.    Tenth  U.  S.  Census. 
SCHUBERT,   MAX.  —  Die  Cellulosefabrikation.       Berlin,    1892.       Fischer    & 

Heilmann. 

TOMLIXSON.  —  The  Manufacture  of  Paper. 
VETILLART. — Etudes  sur  les  Fibres  Vegetales.    Paris,  1876. 
WATT,  ALEX.  —  The  Art  of  Paper-making.    London,  1890. 
WIESXER,    DR.    JULIUS.  —  Die    Mikroscopische   Untersuchung    des   Papiers. 

Vienna,  1887. 


INDEX. 


REFERENCES  ARE  TO  PAGES. 


Absorption  apparatus,  203. 
Behrend,  223. 
Catlin,  217. 
Efcraan,  210. 
Frank,  223. 
Francke,  218. 
McDougall,  214,  216. 
Mitscherlich,  205. 
Neraethy,  220. 
Partington,  215. 
Ritter-Kellner, 

tank  apparatus,  212. 

towers,  218. 
tower  systems,  204. 
Wendler-Spiro,  221. 
Wheelwright,  215. 
Accent  of  chemical  terms,  465,  468. 
Acetate  of  alumina,  77. 
lead,  92,397. 

density  of  solutions,  494. 
Acetates,  analysis  of,  397. 
Acetic  acid,  analysis,  357. 
density  of  solutions,  492. 
use  in  bleaching,  293. 
Acid,  acetic,  analysis,  357. 
,      density  of  solutions,  492. 

use  in  bleaching,  293. 
alkali-cellulosexanthic,  470. 
antimouic,  89. 
arsenic,  61. 
arsenious,  60. 
benzole,  139. 
boracic,  57. 
boric,  57. 
carbonic,  32. 
carminic,  322. 

cellulose-thiosulphocarbonic,  468,. 
chloric,  54. 
chlorous,  54.. 
cinnamic,  139. 
cyauhydric,  35. 
free,  action  on  cellulose,  282. 

in  alum,  311. 
det.  of,  380. 

in  paper,  437. 

In  sulphite  liquor,  209,  225. 
hydrochloric,  49. 

analysis,  355. 

density  of  solutions,  491. 


503 


Acid,  hydrofluoric,  56. 
hypochlorous,  51. 
hyposulphurous,  44. 
muriatic,  49. 
analysis,  355. 
density  of  solutions,  491. 
nitric,  30. 

analysis,  356. 
density  of  solutions,  490. 
Nordhausen,  47. 
oxalic,  analysis,  358. 

density  of  solutions,  483. 
perchloric,  55. 
polythionic,  47. 
pyroligneous,  analysis,  357. 
sulphites,  41. 
sulphuric,  45. 
analysis,  353. 
density  of  solutions,  $88. 
in  burner  gas,  197. 
in  paper-testing,  443. 
prep,  of  different  strengths,  488. 
in  sulphite  liquor,  4M. 
sulphurous,  40. 

action  upon  life,  274. 
action  upon  throat  anfti  lungs,  274. 
analysis,  412. 
density  of  solutions,  498. 
sylvic,  139. 
thionic,  47. 
fhiosulphuric,  45. 
waters,  334. 
Acids,  analysis  of,  353. 

definition,  15. 

Adansonia,  composition  of  bast,  128. 
Agalite  (Fig.  69),  316,  440. 
Agate,  58. 
Agave,  129. 
Air,  29. 

in  wood  cells,  137. 
Air-dry ipulp,  449. 

calculation  of,  451. 
Alabaster,  73. 
Alcohol,  106. 

density  of  solutions,  499. 
Alfa,  131. 
Algse,  331-337. 
Alkali,  analysis,  359. 
by  electrolysis,  460. 


504 


INDEX. 


Alkali,  cellulose,  408. 

manufacturing,  65. 

metals,  63. 

in  soda  pulp,  289. 
Alkaline  earths,  analysis,  359. 

metals  of,  69^ 
Aloe  fibre,  129. 
Alternating  current,  456. 
Alum,  77. 

ammonia,  78. 

potash,  78. 

density  of  solutions,  495. 
Alum  (sulphate  of  alumina),  309. 

analyses  of,  310. 

analysis  of,  375. 

density  of  solutions,  496, 497. 

free  acid,  det.  of,  380. 

manufacture  of,  77. 

moisture  in,  382. 

preservative  effect  on  size,  303. 

sizing  test  for,  380. 
Alumina,  76. 
Aluminate  of  soda,  307. 
Alumine,  fibrous,  317. 
Aluminum,  76. 

acetate,  77. 

bleach  liquor,  295. 

chloride,  action  on  cellulose,  282. 

hydrate,  77. 

hydroxide,  77. 

oxide,  76. 

sulphate,  see  Alum. 
Amalgams,  63,  97. 
Amethyst,  58. 

color  of,  82. 
Ammonia,  30, 69. 

analysis  of,  361. 

density  of  solutions,  493. 

water,  30,  69. 
Ammonia  alum,  77. 
Ammonium,  68. 

hydrate,  analysis,  361. 
density  of  solutions,  493. 

hydroxide,  69. 

sulphate,  60. 
Ampere,  454,  455. 

law  of,  7. 
Amyloid,  107. 
Analysis,  chemical,  348. 

volumetric,  353. 
Anion,  def.,  453. 
Anode,  def.,  453. 

use  of  gas  carbon  for,  460. 
Andreoli  process,  4(>0. 
Auatase,  86. 
Anhydrides,  def.,  16. 
Anhydrite,  73. 
Aniline  colors,  325. 
analysis  of,  401. 

red,  325. 

sulphate,  445. 


Aniline  sulphate  for  paper-testing,  443. 
Animal  size,  301. 

first  use  of,  434. 
Annaline,  317. 
Antichlor.281,283. 

analysis  of,  395. 

Hosford's,  284. 
Antimonic  anhydride,  89. 

chloride,  88. 

sulphide,  88. 
Antimoiious  antimonate,  88. 

chloride,  88. 

hydride,  88. 

oxide,  88. 

oxychloride,  88. 

sulphide,  88. 
Antimony,  88. 

group,  88. 
Apatite,  73. 

Apparatus  for  analyslu,  348. 
Aqua  ammonia,  30. 

density  of  solutions,  493. 
Aqua  fortia,  30. 

density  of  solutions,  490. 
Arithmetic,  chemical,  18. 
Argentic  oxide,  96. 
Argentous  oxide,  95. 
Arsenic,  60. 

acid,  61. 

in  aniline  colors,  60. 

in  hides,  303. 

in  wall  paper,  60. 
Arsenide  of  cobalt,  83. 
Arsenite  of  soda,  preservative  for  size,  303. 
Arsenious  acid,  60. 
Artificial  silk,  111. 
Asbestos,  74. 
Ash  in  paper.  437. 

in  pulp,  438. 
Aspen, 145. 
Atomic  theory,  5. 

weights,  8. 

table  of,  486. 
Atoms,  5. 
Auramine,  326. 

Bacteria,  a38. 

iron,  332. 

jelly,  338. 

Baeyer,  cellulose  and  chlorine,  113. 
Bagasse,  132. 
Baking  soda,  65. 
Balsam,  143. 
Balsams,  138, 139. 
Bamboo,  i:>2. 
Barium,  70. 

hydrate,  70. 

hydroxide,  70. 

oxide,  70. 

peroxide,  70. 

sulphate,  70. 


INDEX. 


505 


Bark,  140. 

coloring  matter  of,  141. 

mulberry,  128. 

tannin,  141. 
Baryta,  caustic,  70. 
Bases,  def.,  15. 

det.  of  in  sulphite  liquors,  414. 
Basic  alum,  312. 

lead  chromate,  92. 
Bass  wood,  147. 
Bast  fibres,  121. 

characteristics  of,  122. 
Bauxtte,  77. 
Beadle,  cellulose,  derivatives,  468. 

formula  for  size,  805. 
Beauine  hydrometer,  482,  483. 
Becquerel,  electrolysis  of  chlorides,  457. 
Beech,  14(5. 
Belgian  flax,  124. 
Benzole  acid,  139. 
Berlin  blue,  400. 
Beryllium,  75. 

Bevan,  cellulose  derivatives,  408. 
Bibliography,  501. 
Bicarbonate,  ferrous,  81. 

of  soda,  371. 
Bichromate  of  potash,  85,  398. 

of  soda,  398. 
Birch,  paper,  147. 

white,  147. 
Bismuth,  89. 

nitrate,  89. 

terchloride,  89. 
fMsulphide  of  carbon,  48. 

action  on  cellulose,  408. 
Bisulphites,  41. 
Bisulphite  of  lime,  184. 

liquor,  analyses  of,  226-228. 
analysis,  412. 
mfg.,  190. 

of  magnesia,  184. 

of  soda,  184. 

Black  ash,  analysis  of,  370. 
Black  liquor,  analysis  of,  165. 
Black  spruce,  142. 
Black  willow,  148. 
Blast  furnace,  80. 

lamp,  Russian,  351. 
Bleach,  consumed  by  water,  332. 

liquid  chlorine,  296. 

liquor,  279. 

aluminum,  295. 
Crouvelle's,  295. 
magnesium,  294. 
Ramsey's,  295. 
Wilson's,  295. 
zino,  295. 

oxygen,  298. 

ozone,  298. 

removal  from  cellulose,  282. 

sulphurous  acid,  299. 


Bleaching,  275. 

acid,  use  of  in,  292. 

chloriuation  of  cellulose  in,  285. 

Cloudman  process,  290. 

ground  wood,  294. 

Herrnite  process,  457. 

hot,  281. 
Bleaching  jute,  294. 

rags,  281. 

wood  fibre,  281. 
Bleaching-powder,  275. 

analysis  of,  391. 

composition  of,  278. 

consumption  of,  280. 

deterioration  of,  277, 

introduction  of,  276. 

manufacture  of,  52. 
by  electrolysis,  460. 

preparation  of  solution,  279. 

properties,  276. 

strength  of,  277. 

Bleaching-salt,  Varrentrapp's,  295. 
Blotting-paper,  capillary  power,  436. 
Blowpipe,  oxyhydrogen,  28. 
"  Blue  Billy,"  40. 

composition  of,  177. 
Blue  dyes,  326. 

stone,  93,  384. 

vitriol,  93. 
Bevilor,  sulphite,  see  Digester. 

vomiting,  157. 
Boiler  scale,  383, 41 2. 

composition  of,  334. 
Boiling-point  of  water,  165. 
Boiling  rags,  151. 

Boiling  wood  by  sulphite  process,  250. 
Boracio  acid,  57. 
Borax,  57,  05. 
Boric  acid,  57. 
Boron,  57- 
Boron  fluoride,  57. 
Bottger  and  Otto,  discovery  of  guncotton, 

106. 

Brandt,  electrolysis  of  sea-water,  457. 
Britannia  metal,  88. 
Bromine,  55. 
Brookite,  86. 
Bronze,  8S. 

digesters,  239. 
Brown  dyes,  326. 
Buckeye,  148. 

Buddeus,  waste  sulphite  liquors,  271. 
Burette,  349. 
Burgess,  Hugo,  electrolysis  of  chlorides, 

457. 

Burnett's  disinfecting  solution,  75. 
Burning  of  pulp,  252. 

Cadmium,  75. 

Cajsium,  68. 
Calamine,  74. 


506 


INDEX. 


Calcium,  71. 
carbonate,  72. 

see  also  Carbonate  of  Lime, 
chloride,  72,  390. 

density  of  solutions,  499. 

in  paper,  437. 

in  pulp,  283. 
hydrate,  71,  72. 

analysis  of,  362. 

density  of  milk  of  lime,  498. 
hydroxide,  71. 
hypocblorite,  391. 

see  also  B lea  chin  g-powder. 
hyposulphite,  45. 
Carbon,  31. 

bisulphide,  48. 

action  on  cellulose,  468. 
dioxide,  32. 
monoxide,  32. 
and  nitrogen,  35. 
and  oxygen,  32. 
and  sulphur,  48. 
Carbonate  of  iron,  80. 
of  lime,  72. 

analysis,  374. 

formation  in  causticizing,  174. 

in  towers,  204. 
water,  333. 
of  magnesia,  74. 

analysis,  374. 

in  water,  330. 
of  potash,  64. 

analysis,  373. 
Calcium  oxide,  71,  72. 

analysis,  362. 

see  also  Lime, 
phosphate,  73. 
sulphate,  73. 

filler  for  paper,  316-318. 

see  also  Lime,  Sulphate  of . 
sulphite,  42. 

use  as  antichlor,  284. 

in  pulp,  270. 

see  also  Lime,  Sulphite  of . 
thiosulphate,  use  as  antichlor,  285. 
Calomel,  97. 
Cambium  layer,  135. 
Canary  paste,  398. 
yellow,  85,  398. 
Caj>acity,  measures  of,  478. 
Carbohydrates,  34, 104. 
Carbonate  of  soda,  65. 
analysis,  367. 
causticizing,  173-175. 
density  of  solutions,  494. 
rafg.,  65. 
use  in  treating  picker  seed,  156. 

rag-boiling,  103. 

sulphate  process,  178. 

sulphite  process,  230. 
of  zinc,  75. 


Carbonate  of  zinc,  analysis,  375. 
Carbonates,  33. 

analysis,  367. 
Carbonic  acid,  32. 

anhydride,  32. 
Carbonizing  wool,  114. 
Carmichael  process,  460. 
Caiminic  acid,  323. 
Carnelian,  58. 
Casein  sizing,  307. 
Casserole,  350. 
Cassiterite,  86. 
Cast-iron  digester,  232. 
Cathion,  def.,  453. 
Cathode,  def.,  453. 

use  of  iron  for,  460. 
Caustic  ash,  analysis,  369. 

baryta,  70. 

potash,  04. 
analysis,  361. 

soda,  64. 

analysis,  359. 
density  of  solutions,  493. 
Caustic  soda,  mfg.,  65. 

use  in  making  size,  304. 

preventing  boiler-scale,  335. 
soda  process,  161. 
sulphate  process,  179. 
treating  rags,  155. 

straw,  159. 
Celestine,  47. 
Cellulose,  103. 

and  chlorine,  112. 
oxygen,  113. 

effect  of  heat  upon,  115. 

fermentation  of,  115. 

Mercerized,  115. 

processes  for  isolating,  151. 
Cellulose  acetate,  108. 

benzoate,  470. 

nitrates,  109. 

thiocarbouates,  468. 
Celsius  thermometer,  479. 
Cemeat,72. 
Cement  linings,  246. 

Curtis  &  Jones,  250. 

Kellner,  246. 

Russell,  247. 

\tenzel,  246. 

Centigrade  thermometer,  479. 
Century  plant,  fibre  of,  129. 
Cerium,  79. 
Chalk,  analysis,  374. 
Chalybeate  waters,  81. 
Chemical  changes,  def.,  3. 
Chemistry,  def.,  3. 

organic,  def.,  35. 
Chestnut,  148. 
Chili  saltpetre,  65, 396. 
China  grass,  128. 
Chloric  acid,  54. 


INDEX. 


507 


Chloride  of  aluminum,  action  on  cellulose, 
282. 

of  calcium,  390. 

density  of  solutions,  499. 

ferric,  391. 

of  gold,  98. 
"  Chloride  of  Litae,"  275. 

see  also  Bleaching-powder. 
Chloride  of  magnesium,  389. 
in  Hermite  process,  457. 
in  water,  333. 

of  potash,  64. 

of  platinum,  98. 

of  sodium,  65. 
analysis  of,  386. 
density  of  solutions,  482. 

of  zinc,  75. 
Chlorides,  action  on  cellulose,  282. 

analysis  of,  386. 

in  paper,  437. 
Chlorine,  49. 

action  upon  coloring  matters,  27G. 

liquid,  296. 

mfg.  by  electrolysis,  453. 
Chlorine  and  cellulose,  112. 

and  hydrogen,  49. 

and  nitrogen,  55. 

and  oxygen,  50. 

and  sulphur,  55. 
Chlorine,  anhydrides  of,  61. 

dioxide,  61. 

hydrate,  49. 
Chlorates,  54. 

Chlorinated  compounds  in  bleached  cellu- 
lose, 285. 

Chlorinated  soda,  394. 
Chlorites,  54. 
Chlorophyll,  117. 
Chlorous  acid,  54. 
Choke-damp,  32. 
Chrome  yellow,  321,398. 
Chromate  of  lead,  85,  92,  321,  398. 

of  potassium,  84. 
Chromates,  analysis  of,  398. 
Chromium,  84. 

compounds,  84. 
Cinnabar,  37. 

Cinnamic  acid,  in  resins,  139. 
Clark  process,  335, 406. 
Classification  of  papers,  420. 
Clay,  58,  77. 

composition  of,  316. 

determination  of,  in  paper,  439. 

use  as  paper-filler,  315. 
Clay  iron-stone,  80. 
Cloudman's  bleaching  apparatus,  290. 
Coal-tar  colors,  325. 
Cobalt,  83. 

compounds  of,  83. 
Cochineal,  322. 
Coooanut  fibre,  128. 


Cohesion,  6. 
Coir  fibre,  128. 
Coke,  31. 
Collodion-,  111. 
Colophony,  139. 
Color  furnishes,  ;i28. 

of  paper,  320. 

of  pulp,  266. 

of  water,  330. 
Coloring,  320. 
Coloring  matter  of  hark,  141. 

of  cotton,  121. 

of  knots,  141. 
Colors,  ash  of  mineral,  440. 

substantive,  320. 
Columbiuna,  90. 
Combined  rosin,  419. 
Combustion,  26,  &i. 

spontaneous,  26. 
Compounds,  7,  10. 

Condensed  water  in  sulphite  process,  255. 
Coniferous  trees,  wood  of,  134. 
Connecticut  River,  color  of  water,  331. 
Conservation  of  energy,  3. 
Continuous  current,  455. 
Copper,  l>2.  , 

pyrites,  198. 

sulphate,  384. 
Copperas,  81,  385. 
Coprolites,  73. 
Cork,  141. 
Corundum,  76. 
Cotton,  121. 

threads,  strength  of,  289. 

waste,  157. 
Cottonwood,  145. 
Craney  process,  460. 
Cream  of  tartar,  04. 
Crenothrix,  332. 
Crocker  process,  230. 

Cross  and  Bevan,  action  of  chlorine  on 
cellulose,  112. 

exam,  of  fibres,  123,  124. 

lignification,  118. 
Cross,  Bevan,  and  Beadle,  new  cellulose 

derivatives,  468. 

Crouvelle's  bleaching-liquor,  295. 
Crown  filler,  317. 
Cryolite,  57,  77. 
Current,  electric,  454. 
Current  efficiency,  454. 
Curtis  &  Jones  lining,  250. 
Cutton  process,  460. 
Cyanhydric  acid,  35. 
Cyanogen,  35. 
Cypress,  146. 

Dalton,  atomic  theory,  5. 
De  Chardonnet,  artificial  silk,  111. 
Definite  proportions,  9. 
Deliquescence,  64. 


508 


INDEX. 


Density  of  woods,  137. 

Dervaux  filter,  344. 

Desiccator,  351. 

Dextrin,  106,  114. 

Diamond,  31. 

Diaphragm,  use  in  electrolysis,  460. 

Didymium,  79. 

Difference  of  potential,  454. 

Digesters,  162,  232. 

bronze,  239. 

cement-lined,  246. 

emptying  of,  260, 263. 

enamel-lined,  243. 

experimental,  269. 

lead-lined,  232. 

Mitscherlich,  242. 

Salomon-Briingger,  243. 

valves  for,  240. 
Dinitrocellulose,  110. 
Dirt  in  paper,  423. 

in  pulp,  267. 

Discs,  use  of  in  Mitscherlich  process,  100. 
•Dithionates,  47. 
Dolomite,  227. 
Drying,  loft,  303. 
Duramen,  136. 

Durin,  cellulosic  fermentation,  116. 
Dyes,  320-322. 

dilutions  of,  327. 

testing  of,  326, 

Earth  metals,  76. 

Eau  de  Javelle,  296,  394. 

de  Labarraque,  296. 
Eder,  nitrogen  in  pyroxylins,  110. 

prep,  of  cellulose  penta-uitrate,  110. 
Edge-runner  for  working  straw,  161. 
Ekinan  furnace,  194. 
modified,  195. 
lining,  237. 
process,  185. 
towers,  210. 
Electric  bleaching,  452. 
Electricity,  conduction  by  liquids,  4~2. 
Electric  current,  analogy  to  flowing  water, 

454. 

effect  of,  452. 
Electrical  units,  454. 
'Electrolysis,  453. 
conditions  of,  456. 
.theory  of,  456. 
Electrolytes,  def.,  453. 
Electrolytic  processes,  452. 
efficiency  of,  462. 
general  features  of.  460. 
Electrolyzer,  Hermite,  457. 
Electromotive  force,  454. 
Elements,  chemical,  5,  7. 
metallic,  62. 
non-metallic,  25. 
table  of,  486. 


Elements  of  wood,  133. 
Emerald,  75. 
Emery,  76. 
E.  M.  F.,  454. 

Energy,  conservation  of,  3. 
Engine  sizing,  304. 
English  test  for  alkali,  360. 
Eosin,  326, 
Epsom  salts,  47. 
Equations,  17. 
Equivalents,  13. 
Erbium,  79. 
Esparto,  131  . 

treatment  of,  157. 
Euchlorine,  51. 
Evaporation,  multiple  effect,  166. 

open  pan,  165. 
Evaporator,  Gaunt,  169. 

Potion,  173. 

Yaryan,  Ui6. 

Examples  in  chemical  arithmetic,  19. 
Expansion  of  -lead,  232. 
Experimental  digester,  269. 

Fahrenheit's  thermometer,  479. 
Fermentation^  decomposition  of  celluloso 
by,  115. 

formation  of  cellulose  by,  116. 
Ferric  chloride,  81. 

nitrate.,  397. 

oxide,  81. 

salts,  del,  15. 

Ferricyanide  of  potassium,  35. 
Ferrocyanide  of  potassium,  35. 
Ferrous  bicarbonate,  81. 

salts,  def.,  15. 

sulphate,  385. 
Fibres,  117. 

bast,  121. 

chemical  examination; 

.derived  from  whole  stems  or  loaves,  129. 
from  wx>od,  132. 

fungoid  growth  on,  269. 

microscopical  examination,  441. 

staiinng  effects,  443. 

standard  mixtures,  444. 
Fibrous  alumine,  317. 

tests  for  in  paper,  439. 
Fillers,  mineral,  314. 
Filter,  .Dervaux,  34£. 

gravity,  338. 


pressure,  341. 

Warren,  v838. 

Filter  paper,  analysis  of,  287. 
Filter-beds,  837. 
Filtration,,  336. 
Filaments,  023. 
Fir,  white,  143. 
Fla«,124. 
Flax,  New  Zealand,  Jflf. 


INDEX. 


509 


Flint,  58. 

Flint  glass,  92. 

Flowers  of  sulphur,  36. 

Fluoride  of  boron,  57. 

Fluorine,  56. 

Fluorspar,  56. 

"Fool's- gold,"  38. 

Fracture  length  of  paper,  425. 

how  calculated,  426. 

Frank,  Dr.,  action  of  waste  sulphite  liquors 
on  animal  life,  273. 

sulphite  liquor  apparatus,  223. 
Free  acid  in  alum,  311. 

in  sulphite  liquor,  208. 

rosin,  determination  of,  418. 
Freiberg  pyrites  burner,  198. 
French  white,,  analysis  of,  374. 
Fuchsine,  325. 
Fuel  value  of  woods,  138. 
Fungoid  growth  in  fibre,  2(59. 

Galena,  37,  91. 
Gallium,  94. 

Gas-cooler,^\£heeTwright,  208. 
Gas  pressure,  7. 

in  sulphite  process,  252. 
Gas  recovery,  261. 
Gelatine,  302. 

Gemmell,  moisture  in  pulp,  451. 
German  silver,  84. 
Girard,  hydration  of  cellulose,  114. 
Gladstone,  action  of  soda  upon  cellulose 

115. 

Glass,  58. 
Glauber's  salt,  65. 
Glucinuni,  75. 
Glucose,  106, 114. 
Glue,  302, 

Glycerine,  density  of  solutions,  498. 
Godeffroy,  det.  of  ground  wood,  446. 
Gold,  98. 

ftoodaie,  bast-fibres,  122. 
Graham  digester,  2o8. 
Graphite,  31. 
Graphic  symbols,  14. 
Gravity  filters,  338. 
Gray  pine,  142. 
Green  dyes,  326. 

vitriol,  81. 

Greenwood  process,  460. 
Gritfm,  Martin  L.,  moisture  in  pulp,  450. 
Grit  in  paper-fillers,  315. 
Ground  wood,  bleaching  of ,  294. 

samplingr  447. 

tests  for,  445. 
Growth  o*  wood ,  135. 
Gum  reshis,  13&. 
Gum,  sweet,  145. 
Gums,  120. 
GuneoUo.n,  109. 
Gypsum,  47,  73. 


Gypsum  paper-filler,  317. 

det.  of,  439. 
Hackmatack,  144. 
Haermatite,  80. 
Halogens*  57. 

compounds  of,  57. 
Hard  water,  72,  329. 
Hardness,  test  for,  in  water,  403. 
Heart  wood,  136. 
Heat,  6. 

latent,  7. 

relations  of  atoms  to,  8. 

specific,  7. 

ui>it  of,  7. 

units  developed  by  combustion,  33. 
Heavy  spar,  47,  70. 
"  Heavy  lead  ore,"  91. 
Hemlock,  144. 
Hemp,  126. 

sisal,  129. 

sunn,  127. 
Henequin,  129. 
Hermite  process,  457. 
Herzberg,  ash  in  pulps,  438. 

plate- of  fibres,  132. 

Hewitt  and  Mond,  causticizing  process,  175. 
Hexaottrocellulose,  110. 
HohneT,  lignin  reactions,  445. 
Holland  and  Richardson  process,  460. 
Horse  power,  electrical,  456. 
Hosford^s  antichlor,  284. 
Hydrate  of  aluminum,  77. 

of  calcium,  71. 

of  magnesium, .74. 
Hydrates,  def.,  15. 
Hydraulic  lime,  72. 
Hydrocarbons,  31. 
Hydrocellulose,  114, 437. 
Hydrochloric  acid,  49. 

analysis  of,  355. 

density  of  solutions,  491. 

use  in  bleaching,  292. 
Hydrofluoric  acid,  66. 
Hydrogen,  27. 

and  chlorine,  49. 

peroxide,  29. 
mfg.,  70. 
use  as  antichlor,  285. 

sulphide,  38. 
Hydrolysis,  def.,  182. 
Hydrometer,  Beaume,  482,  483. 

Twaddle's,  484. 
Hydroxide  of  alumina,  77. 

of  zinc,  74. 
Hypochlorite  of  aluminum,  295. 

of  calcium,  275,  301. 

of  magnesium,  294,  394. 

of  potash,  296,  394. 

of  soda,  29fi,  394. 

of  zinc,  295. 
Hypochlorites,  prep,  by  electrolysis,  452. 


510 


Hypochlorous  acid,  fil,  292. 
Hyposulphite  of  soda,  45,  283. 
Hyposulphurous  acid.  44. 

Indian  red,  400. 

Indium,  94. 

Injectors  for  transferring  liquor,  231. 

Iodine,  5(5. 

solution  for  paper-testing,  443. 
Ion,  def.,  453. 
Intensity  currents,  455. 
Iridium,  100. 
Irish  flax,  124. 
Iron,  80. 

in  alum,  311. 

bacteria,  332. 

pyrites,  198. 

wood,  138. 
Isinglass,  302. 
Italian  hemp,  126. 

Javelle  water,  394. 

Jung  and  Lindig  lining,  245. 

Jute,  125. 

bleaching  of,  294. 

treatment  of,  293. 
Kaolin,  58. 
Kellner,  cement  lining,  246. 

filtering-tower,  201. 

sizing,  313. 
Kellogg  lamp,  351. 
Kier,  the  Mather,  153. 
Knofler  oven,  449. 
Knots,  140. 

removing  from  wood,  189. 
Kupfer-nickel,  84. 

Labarraque's  solution,  394. 
Lampblack,  31. 
Lanthanum,  79. 
Larch,  144. 
Latent  heat,  7. 
Lavoisier,  3.. 
Law  of  Ampere,  7.. 

of  definite  proportions,.  9. 
of  multiple  proportions,  12. 
Ohm's,  455. 
Load,  91. 

action  of  acids  upon,  233. 
burning,  241. 
linings,  232. 
Ekman,  237. 
Francke,  234. 
Graham,  238. 
Makin,  235. 
Mitseherlich,  242. 
Partington,  234,  236. 
Ritter-Kellner,  237. 
Kussell,  235. 
Springer,  236. 
Wheelwright,  238. 


Lead  acetate,  92,  397. 

density  of  solutions,  494. 

chromate,  85,  92. 
testing,  398. 
use  in  coloring  paper,  321. 

sugar  of,  92,  397. 

density  of  solutions,  494. 
Leblanc  process,  65. 
Length,  measures  of,  478. 
Leonhardi's  test  for  sizing,  436. 
Le  Sueur  and  \Vaite  process,  460. 
Liber-fibres,  123. 
Light,  action  on  rosin  size,  306. 
Lignifted  fibre,  tests  for,  445* 
Lignification,  118. 
Lignin,  118. 
Liguireose,  119. 
Lignite,  31. 
Lignone,  119. 
Lignose,  119. 
Lime,  71. 

analysis  of,  362. 

composition  of,  for  causticizing,  174. 

for  rag-boiliug,  152. 

for  sulphite  liquor,  227. 

det.  of  in  sulphite  liquor,  414. 

hydraulic,  72. 

milk  of,  71. 
density,  498. 

reclaimer,  175. 

water,  71. 

Lime,  carbonate  of,  72. 
analysis,  374. 
in  water,  338. 

sulphate  of,  73,  191. 

sulphite  of,  191,  229,  253. 
Limestone,  72. 

analysis  of,  374. 

use  in  tanks,  212. 

in  (towers,  204. 
Linen,  124. 

Liquor-making,  sulphite,  190. 
Litharge,  91. 
Lithi  um>68. 
Loading  paper,  314. 
Locust,  148. 
Lunar  caustic,  96. 

Mactear,  tabulated  view  of  alkali  mfg.,87. 
Magenta,  325. 
Magnesia,  74. 

analysis,  365. 

bleach  liquor,  294- 

det.  of  in  sulphite  liquors,  414. 

use  in  Ekman  process,  187,  210. 
Magnesite,  analysis,  374. 
Magnesium,  73. 

carbonate,  analysis,  374. 

chloride,  389. 

density  of  solutions,  501. 
electrolysis  of,  458. 


INDEX. 


611 


Magnesium  hydrate,  74.  365. 

hypochlorite,  29*,  394. 
by  electrolysis,  458. 

oxide,  74, 187,  210. 

silicate,  74. 

use  as  paper-filler,  316,  440. 

sulphate,. 74,  384. 
Magnetic  iron  ore,  80. 

metals,  79. 
Magnetite,  80. 
Makin  lining;  235. 
Malachite  green,  326. 
Manganese,  82. 
Manganite,  82. 
Manila,  126. 
Maple,  silver,  140. 
Marble,  analysis,  374. 
Marsh  gas  from  cellulose,  116. 
Mass,  d&.,  4. 
Mather  Kler.  153. 
Matter,  3. . 

conservation  of,  3. 

properties  of,  5. 

states  of,  6. 
Mauvein,  325. 
McDougall,  digester  lining,  235. 

liquor  apparatus,  212,  217. 
Measures,  metric  system,  4,  478. 
Meerschaum,  74. 
Mercerized  cellulose,  115. 
Mercury,  97. 

compounds  of,  97. 

Merrimac  River,  color  of  water,  331. 
Metals,  62. 

alkali  group,  63. 

antimony  group,  88. 

of  alkaline  earths,  69. 

earth,  76. 

iron  group,  79. 

lead  group.  90. 

magnesium  group,  73. 

magnetic,  79. 

noble,  93. 

silver  group,  95. 

tin  group,  85. 
Metantimonic  acid,  89. 
Methyl  violet,  326. 
Metric  system,  478. 
Microscope,  441. 
Microscopical  examination  of  fibres,  441. 

of  paper-fillers,  314. 
Milk  of  lime,  71. 

density  of,  498. 

Millon's  reagent,  test  for  auimal  size,  432. 
Mineral  colors,  321,  398. 
Mineralization  of  cell-wall,  117. 
Minium,  91. 
Mitscherlieh  process,  digester,  242. 

gas  recovery,  262. 

boiling,  256. 

pulp,  267. 


Mitschetlich  process,  pyrites  burner,  199. 

stamp  mill,  263. 

sulphur  furnace,  196. 

tower 'system,  205. 
Mitscherlieh  sizing  process,  313. 
Mixtures  and  compounds,  10. 
Moisture  in  pulp,  446. 
Molecules,  5. 
Molybdenite,  87. 
Molybdenum,  87. 

"  Money  value  "  test  for  dyes,  402. 
Monosulphite  of   calcium,  formation   of, 
228,  253. 

incrustation,  229,  253. 

removal  of,  230. 
Mordants,  320. 
Mortars,  72. 
Mosaic  gold,  86. 
Mulberry  tree,  128. 
Mulder,  formation  of  glucose,  116. 
Mtiller,  A.,  ash  in  fibres,  438. 
Miiller,  Hugo,  analysis  of  cotton,  121. 

esparter,  131. 

flax,  124. 

jute,  125. 

hemp,  126. 

manila,  127. 

«unn  hemp,  127. 

woods,  140. 

Multiple-effect  evaporation,  186. 
Muriatic  acid,  49. 

analysis,  355. 

density  of  solutions,  491. 

Naphthol,  326. 
Nascent  state,  17. 
Negative  pole,  455. 
N&nethy  liquor  apparatus,  220. 
New  York  Filter  Co.'s  filter,  341. 
New.  Zealand  flax,  127. 
Nfckel,  and  compounds  of,  84. 
Nitrates,  31. 

analysis  of,  395. 
Nitrate  of  iron,  397. 

of  lead;  92. 

of  potash,  64,  395. 

of  silver,  96. 

of  soda,  65,  396. 
Nitric  acid,  30. 

analysis  of,  356. 

density  of  solutions,  490. 
Nitrogen,  29. 

and  carbon,  35. 

and  chlorine,  55. 

and  oxygen,  30. 

and  sulphur,  48. 
Noble  metals,  95. 
Nomenclature,  14. 
Nordhausen  acid,  47. 
Normal  paper,  420. 
Normal  solutions,  352. 


512 


INDEX. 


Korton,   Dr.  L.   M.,  moisture   in   pulp, 
451. 

Ochres,  400. 

Ohm,  def.,  455. 

Ohm's  law,  455. 

Oil  of  vitriol,  46. 

Oleo-resins,  138. 

Onyx,  58. 

Open-pan  evaporation,  165. 

Orange  mineral,  91,  399. 

Osmium,  100. 

Ovens,  drying-,  448. 

Oxalic  acid,  analysis,  358. 

density  of  solutions,  483. 
Oxides,  26. 

of  aluminum,  76. 

of  antimony,  88. 

of  arsenic,  60. 

of  barium,  70. 

of  cadmium,  75. 

of  calcium,  71. 

of  carbon,  32. 

of  chlorine,  50. 

of  cobalt,  83. 

of  copper,  92. 

Of  chromium,  84. 

of  indium,  94. 

of  iron,  80. 

of  lead,  91. 

of  magnesium,  74. 

of  manganese,  82. 

of  mercury,  97. 

of  molybdenum,  87. 

of  nickel,  84. 

of  nitrogen,  30. 

of  potassium,  63. 

of  silicon,  58. 

of  silver,  95. 

of  sodium.  360. 

of  sulphur,  39. 

of  tin,  85. 

of  tungsten,  87. 

of  vanadium,  90. 

of  zinc,  74. 
Oxidizing  flame,  34. 
Oxycellulose,  113. 
Oxygen,  25. 

mfg.  of,  70. 

use  hi  bleaching,  298. 
Oxyhydrogen  flame,  28. 
Ozone,  27.  , 

bleach,  298. 

Palladium,  99. 
Paper,  ash  in,  437. 

capillary  power  of  blotting,  436. 

chlorides  in,  437. 

classification  of,  420. 

direction  on  machine,  421. 

dirt  in,  423. 


Paper  filler,  det.  of  kind,  439. 

filter,  analysis  of,  287. 

finish  of,  423. 

fracture  length  of,  425. 

free  acid  in,  437. 

ground  vood  in,  445. 

microscopical  examination  of,  44-1. 

norm&l,  420. 

parchment,  107. 

light  and  wrong  sides,  421. 

starch  in,  434. 

strength  of,  424. 

stretch  of,  424. 

testing,  420. 

thickness  of,  424. 

water  marks,  422. 
Paper  birch,  1 47. 

mulberry,  128. 
Parchment  paper,  107. 
Paris  green,  60,  93. 
Paris,  plaster  of,  73. 
Partington  lining,  234,  236. 

liquor  apparatus,  215. 
Partition,  use  of  porous,  in  electrolysis,  453. 
Paste,  92. 

Patents,  list  of  sulphite,  471. 
Pearlash,  analysis  of,  373. 
Pearl  hardening,  316,  439. 

analysis  of,  .383. 

composition  of,  3l7. 
Pelouze,  action  of  nitric  acid  on  cellulose, 

108. 

Peuta-nitro-cellulose,  110. 
Perchloric  acid.  55. 
Permanganate  of  potash,  83. 
Peroxide  of  barium,  70. 

of  hydrogen,  29. 

use  as  antichlor,  285. 
Pewter,  85. 

Phloroglncin,  for  paper-testing,  441,  445. 
Phosphate  of  lime,  73. 
Phosphate  rock,  73. 
Phosphides.  59. 
Phosphor  bronze,  tX),  86. 
Phosphorus,  59, 
Photography,  96. 
Physical  change,  3. 
Physical  properties,  5. 
Picker  seed,  treatment  of,  156. 
Picker  waste,  treatment  of,  I5£. 
Pig  iron,  81. 
Pine,  gray,  142. 

white,  14?*. 
Plaster  of  Paris,  73. 
Platinum,  98. 
Plumbago,  31. 
Poles,  def.,  453. 

of  dynamo,  455. 
Polythionic  acids,  197. 
Poplar,  144. 
Porion  evaporator,  172. 


INDEX. 


513 


Porter-Clark  process,  335. 
Potash,  63. 
caustic,  64. 
analysis,  361. 
density  of  solutions,  495. 
Potash  alum,  77. 

density  of  solutions,  495. 
Potassium,  6b. 

bichromate,  85,  398. 
carbonate,  64. 
chlorate,  54,  64. 
chloride,  64. 
chromate,  84. 
ferricyanide,  35. 
ferrocyanide,  35. 
hydrate,  64,  361,  495. 
hypochlorite,  296,  394. 
nitrate,  64,  395. 
oxide,  63,  361. 
permanganate,  83. 
tartrate,  64. 
Potential,  454. 

Prefixes,  use  in  chemical  terms,  405. 
Preparing  wood,  188. 
Pronunciation  of  chemical  terms,  465. 
Prussian  blue,  35,  321,  400. 
Prussic  acid,  35. 

Pulp,  "  air-dry,"  moisture  in,  449. 
sampling,  447. 
testing  for  moisture,  44(5. 
Pulp,  soda,  161. 

cause  of  bad  odors  in,  38. 
effect  of  traces  of  black  liquor,  289. 
yields,  149. 
sulpha-te,  mfg.,  178. 
sulphite,  analysis  of,  bleached,  287. 
analysis  of  Mitscherlich,  267. 
analysis  of  quick  cooked,  268. 
bleaching,  loss  in,  288. 
blue,  addition  of,  to  bleached,  285. 
burned,  266. 

cause  of  bad  odors  in,  38. 
chlorinated  cellulose  in,  286. 
dirt  in,  267. 

fungoid  growth  on,  269. 
quality,  conditions  affecting,  261, 266. 
yellow  discoloration  on,  283. 
yields,  149,  269. 
Pumping  sulphite  liquor,  230. 
Pyrites,  37,  38. 
'copper,  198. 
iron,  198. 
Pyrites  burner,  Freiberg,  198. 

Mitscherlich,  199. 
Pyrolusite,  82. 
Pyroxylin,  109. 

Quantity  currents,  456. 
Quantivalence,  13. 
Quartz,  58. 
Quicklime,  71. 


Radicle,  def.,  69. 

Rags,  boiling,  etc.,  151. 

Ramie,  127. 

Ramsay's  bleach  liquor,  295. 

Reactions,  17. 

analytical,  18. 

secondary,  453. 

synthetical,  18. 
Recovered  lime,  175. 
Recovery  of  gas,  261. 

of  soda,  158,  164. 
Red  dyes,  325. 
Reducing  flame,  34. 
Resins,  120, 138. 
Retention  of  fillers,  318,  440. 
Retort  sulphur  furnace,  193. 
Rhea,  128. 
Rhodium,  99. 
Ritter-Kellner  filtering-tower,  200. 

lining,  237. 

tank  apparatus,  211. 

tower  system,  218. 
Rock  crystal,  58. 
Rosm,  139. 

combined,  det.  of,  419. 

free,  in  size,  304. 
Rosin  size,  analysis  of,  417. 

composition  of,  305. 

preparation,  305. 

test  for,  433. 
Rotary  furnaces,  170. 

rag  boilers,  151. 

sulphite  digesters,  236. 
Rubbing  test  for  paper,  431. 
Rubidium,  68. 
Ruby,  76. 

Ruby  copper  ore,  93. 
Russell  cement  lining,  247. 

lead  lining,  2,S5. 
Russian  blast  lamp,  351. 
Ruthenium,  99. 
Rutile,  86! 

Safranine,  326. 

Salomon-Brungger  digester,  243. 
Salt  cake,  385. 
Salt,  common,  65. 

analysis  of,  386. 

density  of  solutions,  482. 

electrolysis  of,  453. 
Salt  of  tartar,  373. 
Saltpetre,  64. 

analysis  of,  395. 
Salts,  15. 

Sampling  pulp,  447. 
Sapphire,  76. 
Sapwood,  136. 
Scale,  boiler,  333. 

preventives,  335. 
Scarlet  Hquor,  324. 
Schenck  digester  metal,  239. 


514 


INDEX. 


Schonbein,  discovery  of  explosive  cotton, 

108. 

Schopper  paper-tester,  428. 
Sckuman,  det.  of  rosin  size,  434. 
Schiinck,  wax,  etc.,  in  raw  cotton,  121. 
Schweitzer's  reagent,  104. 
Sea-water,  49. 
Secondary  reactions,  453. 
Seed-hairs,  121. 
Selenite,  73. 
Selenium,  48. 
Serpentine,  74. 
Sesquichloride  of  iron,  391. 
Sesquioxide  of  alumina,  77, 

of  iron,  81. 
Silver,  95. 
Silver  maple,  14(5. 
Silvering  mirrors,  97. 
Silica,  58. 

in  water,  334. 
Silicate  of  magnesia,  74. 

of  soda,  58,  308. 
Silicon,  58. 
Sisal  hemp,  129. 
Size,  det.  of  in  paper,  431. 
rosin,  304. 

action  of  light  on,  306. 
analysis  of,  417. 
composition  of,  305,  306. 
prep,  of,  305. 

with  aluminate  of  soda,  307. 
with  silicate  of  soda,  308. 
Sizing,  301. 

use  of  acid  sulphites,  313. 
casein,  307. 
starch,  319. 
Smalt,  83. 
Soap-stone,  74. 
Soda,  65. 

analysis  of,  367. 
density  of  solutions,  494. 
det  of  in  sulphite  liquor,  416. 
recovery  of,  158, 164. 

sources  of  loss  in,  177. 
Soda  alum,  77. 
Soda,  aluminate  of,  307. 
Soda  ash,  65. 

analysis  of,  367. 
causticiziug,  173-175. 
density  of  solutions,  494. 
Soda,  caustic,  64. 
,  analysis  of,  359. 

density  of  solutions,  493. 
Soda  process  for  wood  fibre,  161. 
boiling,  162. 
causticizing,  173. 

Hewitt  &  Mond  process,  175. 
recovery,  164. 
sources  of  Joss,  177. 
Sodium,  64. 

by  electrolysis,  453. 


Sodium  aluminum  fluoride,  71/" 
biborate,  57,  (55. 
bicarbonate,  65. 

analysis  of,  371. 
bichromate,  398. 
carbonate,  05. 
analysis  of,  367. 
density  of  solutions,  494. 
chloride,  <>5. 

analysis  of,  386. 
density  of  solutions,  482. 
electrolysis  of,  453-459. 
use  in  Hermite  process,  459. 
hydrate,  64. 

analysis  of,  359. 
density  of  solutions,  493. 
hypochlorite,  296,  394.     , 
hyposulphite,  44. 

use  as  autichlor,  283. 
nitrate,  65. 

analysis  of,  396. 
silicate,  58. 

use  in  sizing,  308. 
sulphate,  385. 

sulphite,  use  as  antichlor,  284. 
thiosulphate,  45. 

use  as  antichlor,  283. 
tungstate,  87. 
Soft  water,  329. 
Solder,  86. 
Solids,  mineral  in  water,  407. 

total  in  water,  406. 
Solutions,  normal,  352. 
Solvay  ash,  use  in  sulphite  process,  230. 
Solvay  process,  68. 
Sorghum,  132. 
Specific  gravity,  4. 

and  degrees  Beaume',  482,  483. 
and  degrees  Twaddle,  484, 
Specifio  heat,  7. 
Specular  iron  ore,  80. 
Speiss  cobalt,  83. 
Spelling  of  chemical  terms,  465. 
Sponges,  fresh-water,  331. 
Spontaneous  combustion,  26. 
Springer  lining,  236. 
Spruce,  142. 

analysis  of,  140. 
preparation,  188. 
specific  gravity,  etc.,  138, 
yields,  149,  269. 

Spruce  pulp,  ground  wood,  142. 
soda,  164. 
sulphate,  178. 
sulphite,  267. 

analyses  of,  267,  268,  287. 
Stamp  mill,  263. 
Standard  papers,  442. 
Standard  solutions,  352. 
Stannate  of  soda,  86. 
Starch,  319,  434. 


515 


Steam,  temperature  of,  487. 

Steel,  81. 

Stibine,  88. 

Stochiometry,  18. 

Stock  in  normal  papers,  420. 

Storage  tanks,  231. 

Storer,  fixing  of  nitrogen  by  hum  us,  116. 

Straw,  129. 

treatment  of,  158. 
Strontium,  71. 
Suberin,  141. 

Sublimation  of  sulphur,  197. 
Substantive  colors,  320. 
Sugar  of  lead,  92. 

analysis  of,  397. 

density  of  solutions,  494. 
Sulphates,  47. 

analysis  of,  375. 
Sulphate  of  alumina,  77,  309. 

analysis  of,  375. 

composition  of,  310. 
Sulphate  of  ammonia,  69. 

of  barium,  70. 

of  calcium,  73,  228. 

of  copper,  90,  384. 

of  iron,  81,  885. 

of  lead,  91,  233. 

of  lime,  73. 

in  ash  of  paper,  439. 

in  sulphite  liquor,  191,  22!,  228. 

in  towers,  207. 

in  water,  334. 

paper-filler,  310. 

of  magnesia,  74.  884. 

Of  soda,  65,  366 

of  zioe,  75,  384. 
Sulphate  process,  178. 
Sulphides,  37. 
Sulphites,  41. 
Sulphite  of  lime,  43. 

antichlor,  284. 

cause  of  leaky  tanks,  231. 

cause  of  leaky  valves,  230. 

in  liquor,  209. 

in  Frank  apparatus,  225. 

in  Jung  &  Liudig  lining,  245. 

in  Salomon-Brungger  lining,  243. 

in  sediment,  228. 

in  towers,  207. 

incrustation  in  digester,  253. 
liquor  apparatus,  229. 

precipitation  of,  253. 

solubility,  191. 
Sulphite  of  magnesia,  43. 

in  towers,  188. 
Sulphite  of  soda,  184. 

antichlor,  284. 
Sulphite  liquors,  analysis  of,  412. 

composition  of,  208,  209,  210,  226,  223. 

preparation  of,  190. 

absorption  apparatus,  203. 


Sulphite  liquors,  lime  for,  227. 
pumping,  230. 
storage,  231. 
sulphur  burning,  192. 

waste,  270. 

action  on  life,  273,  274. 
Sulphite  process,  179. 

boiling,  250. 

digesters  and  linings,  232. 

gas  recovery,  261. 

history,  185. 

liquor-making,  190. 

patents,  471. 

preparing  wood,  188. 

theory,  182. 

waste  liquor,  270. 
Sulpho-arsenides,  60. 
Sulphur,  35. 

action  of  8O2  on,  197. 

analyses  of,  192. 

burning,  190,  192. 

filtering-tower,  201. 

flowers  of,  36. 

grades,  37,  192. 

loss  of,  228. 

sublimation,  197. 

yield  of  SO2,  225. 
Sulphur  and  carbon,  48. 

and  chlorine,  55. 

and  nitrogen,  48. 

and  oxygen,  39. 
Sulphur,  compounds  of,  37. 
Sulphur  dioxide,  .40. 
Sulphuretted  hydrogen,  39. 
Sulphuric  acid,  45. 

action  on  lead,  233. 
on  wood,  182. 

analysis  of,  353. 

cause  of  loss  of  sulphur,  229. 

density  of  solutions,  488. 

det,  of  in  sulphite  liquor,  414. 

formation  during  boiling,  361,  185. 
during  sulphur  burning,  190, 191, 196, 
214. 

in  alum,  311. 

prep,  of  different  strengths,  489. 

removal  from  gas,  200, 203. 

use  in  bleaching,  292. 

in  paper-testing,  443. 
Sulphuric  anhydride,  47. 
Sulphurous  acid,  40. 

action  on  life,  274. 
on  sulphur,  197. 

available,  209. 

bleach,  44,  299. 

blowing  off,  252. 

combined,  209. 

density  of  solutions.  498. 

determination  of,  412. 

free,  209. 

gas  pressure,  252. 


616 


INDEX. 


Sulphurous  acid  in  burner  gas,  208. 

in  furnace  gas,  190. 

in  sulphite  liquor,  210,  226,  228. 

in  waste  liquor,  273. 
use  in  pulp-making,  179. 
Sulphurous  anhydride,  40. 
Sunn  hemp,  127. 
Surface  waters,  329. 
Sylvic  acid,  in  resins,  139. 
Symbols,  10. 

graphic,  14. 

Synthetical  reactions,  18. 
Sweet  gum,  145. 

Talc,  74. 

Tamarack,  144. 

Tannic  acid,  test  for  animal  size,  431. 

Tannin  in  bark,  141. 

Tappeiner,  fermentation  of  ceHulose,  115. 

Tartar  emetic,  88. 

Tartar,  salt  of,  analysis,  373. 

Tauss,  effect  of  hot  water  on  cellulose,  115. 

Tellurium,  48. 

Temperature,  6. 

effect  on  sizing,  312. 
Temporary  hardness,  405. 
Terminations  of  chemical  terms,  466. 
Tetranitro-cellulose,  110. 
Thallium,  92. 

Thermometers,  relations  between,  479. 
Thio-derivatives  of  cellulose,  468. 
Th ionic  acids,  47. 

Thiosnlphate  of  calcium,  use  as  antichlor, 
285. 

of  soda,  45. 

Thiosulphuric  acid,  45. 
Thorium,  87. 

Tilghman,  inventor  of  sulphite  process,  179. 
Tin,  85. 
Tinstone,  86. 
Titanium,  86. 
Trache'ids,  132. 

measurements  of,  137. 
Triuitro-cellulose,  110. 
Tungsten,  87. 
Turpeth  mineral,  97. 
Turquoise,  77. 
Twaddle's  hydrometer,  484. 

Ulbricht,  distribution  of  resin  in  wood,  139. 
Ultramarine,  321,  400. 
Unit  of  atomic  weights,  8. 

of  heat,  7,  33. 
Units,  electrical,  454. 

of  weights  and  measures,  478. 
Uraaium,  85. 

Vanadium,  89. 

attraction  of  cellulose  for  compounds 
of,  104. 


Vanadium,  attraction  of  oxycelluiose  for 

compounds  of,  113. 
Vanillin,  test  for,  433. 

in  waste  liquors,  271. 
Varrentrapp's  bleaching-salt,  295. 
Vegetable  cell,  117. 
Venetian  red,  399. 
Verdigris,  93. 
Vermilion,  97. 
Victoria  green,  326. 
Vinegar,  analysis  of  wood,  357. 
Violet  dyes,  32H. 
Vitriol,  blue,  93,  384. 

green,  81,  385. 

white,  75,  384. 
Vitriol,  oil  of,  45. 

analysis,  353. 

density  of  solutions,  488. 

prep,  of  different  strengths,  489. 
Volt,  def.,  454. 
Volume,  def.,  4. 
Volumetric  analysis,  353. 
Vomiting  boiler,  157. 

Warren  filters,  338. 

rotary  furnace,  170. 

Washing  and  bleaching  apparatus,  Cloud- 
man,  290. 
Washing-soda,  (15. 
Waste  sulphite  liquor,  270. 
Water,  29,  329. 

acid,  334. 

analysis,  403. 

Clark's  softening  process,  406. 

collecting  samples,  346. 

color  of,  830. 

effect  upon  bleaching,  290- 

for  manufacturing  purposes,  411. 

hardness  of,  329,  333,  403. 

in  wood,  137. 

organic  and  volatile  matter  in,  407. 

scale-forming,  333. 

sea,  49. 

total  solids,  406. 

volume  used  per  ton  of  paper,  330. 
Water-bath,  351. 

gas,  32. 

marks,  422. 
Water  of  ammonia,  69. 

analysis,  301. 
Waters,  chalybeate,  81. 

surface  and  ground,  329. 
Wax  in  raw  cotton,  121. 

in  straw,  131. 
Weigelt-Reufach,  action  of  waste  liquors  on 

life,  273. 
Weight,  def.,  4. 
Weights,  atomic,  8. 

metric  system,  478. 
Well-thread,  332. 
Wendler  paper-tester,  425. 


INDEX. 


517 


Weridler-Spiro  liquor  apparatus,  221. 
Wenzel  cement  lining.  246. 
Wheelwright  cooler,  203. 

digester,  238. 

liquor  apparatus,  215. 
White  arsenic,  GO. 

birch,  147. 

fir,  143. 

lead,  91. 

pine,  143. 
Whiting,  374. 

Wiesner,  starch  in  ancient  papers,  319. 
Willesden  paper,  105. 
Willow,  148. 

Wilson's  bleach  liquor,  295. 
Witherite,  70. 

Witz,  action  of  oxidizing  agents  on  cellu- 
lose, 113. 
Wood,  132. 

density  of,  137. 

elements  of,  133. 

growth  of,  135. 

heaviest,  138. 


Wood,  moisture  in,  137. 

of  coniferous  trees,  134. 

preparing,  161,  188. 

resin  in,  139. 

Wood-cells,  air  and  water  in,  137, 
Wood-fibres,  133. 
Wood-vinegar,  357. 
Woods,  analyses  of,  140. 

fuel  value,  138. 

Woods  used  in  pulp-making,  141, 149,150. 
Wiirster,  determination  of  starch, 434. 

theory  of  sizing,  304,  433. 

Yaryan  evaporator,  166. 
Yellow  dyes,  326. 
Yttrium.JU 

Zinc,  74. 

bleach  liquor,  295. 

compounds  of,  74,  75. 

sulphate,  analysis  of,  384. 
Zirconium,  86. 
Zylonite,  111. 


t- 


. 

\ 


FIG  66.  —  SOUTH  CAROLINA  CLAV. 


' 


•r-s 


* 


.- 

.  fi;;/ 


^  •         •*     •-  •••   jt 

*  '  *  •;•„;;?' 


FIG.  67.  —  ENGLISH  CHINA  CLAY. 


FIG.  68.  —  LEAMOUR  CLAY. 


FIG.  69.  —  AGALITE. 


FIG.  70.  —  PEARL  HARDENING. 


PIG.  71.  —  FIBROUS  ALUMINE. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 


Return  to  desk  from  which  borrowed. 
This  book  is  DUE  on  the  last  date  stamped  below. 


DEC   13  1947 


SEP 

8Apr'58LW 


LD 


LD  21-100m-9,'47(A5702sl6)476 


7~S 


385548 


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YC   18248 


UNIVERSITY  OF  CALIFORNIA  UBRARY 


